diff --git a/src/main/java/de/studiocode/invui/gui/GUI.java b/src/main/java/de/studiocode/invui/gui/GUI.java
index 871daf3..699b567 100644
--- a/src/main/java/de/studiocode/invui/gui/GUI.java
+++ b/src/main/java/de/studiocode/invui/gui/GUI.java
@@ -4,6 +4,7 @@ import de.studiocode.invui.animation.Animation;
 import de.studiocode.invui.gui.SlotElement.ItemStackHolder;
 import de.studiocode.invui.gui.builder.GUIBuilder;
 import de.studiocode.invui.gui.impl.*;
+import de.studiocode.invui.gui.structure.Structure;
 import de.studiocode.invui.item.Item;
 import de.studiocode.invui.virtualinventory.VirtualInventory;
 import de.studiocode.invui.window.Window;
@@ -195,6 +196,13 @@ public interface GUI extends GUIParent {
      */
     void remove(int index);
     
+    /**
+     * Applies the given {@link Structure} to the {@link GUI}.
+     *
+     * @param structure The structure
+     */
+    void applyStructure(Structure structure);
+    
     /**
      * A method called if a slot in the {@link Inventory} has been clicked.
      *
diff --git a/src/main/java/de/studiocode/invui/gui/builder/GUIBuilder.java b/src/main/java/de/studiocode/invui/gui/builder/GUIBuilder.java
index 8bdfd8e..ca66b13 100644
--- a/src/main/java/de/studiocode/invui/gui/builder/GUIBuilder.java
+++ b/src/main/java/de/studiocode/invui/gui/builder/GUIBuilder.java
@@ -2,17 +2,17 @@ package de.studiocode.invui.gui.builder;
 
 import de.studiocode.invui.gui.GUI;
 import de.studiocode.invui.gui.SlotElement;
-import de.studiocode.invui.gui.SlotElement.ItemSlotElement;
 import de.studiocode.invui.gui.impl.*;
+import de.studiocode.invui.gui.structure.Marker;
+import de.studiocode.invui.gui.structure.Structure;
 import de.studiocode.invui.item.Item;
-import de.studiocode.invui.item.impl.SimpleItem;
 import de.studiocode.invui.item.itembuilder.ItemBuilder;
 import org.bukkit.inventory.ShapedRecipe;
 import org.jetbrains.annotations.NotNull;
 
 import java.util.ArrayList;
-import java.util.HashMap;
 import java.util.List;
+import java.util.function.Supplier;
 
 import static de.studiocode.invui.gui.builder.GUIType.*;
 
@@ -26,9 +26,8 @@ public class GUIBuilder {
     private final GUIType guiType;
     private final int width;
     private final int height;
-    private final HashMap<Character, Ingredient> ingredientMap = new HashMap<>();
     
-    private String structure;
+    private Structure structure;
     
     private List<Item> items = new ArrayList<>();
     private List<GUI> guis = new ArrayList<>();
@@ -39,33 +38,38 @@ public class GUIBuilder {
         this.height = height;
     }
     
-    public GUIBuilder setStructure(@NotNull String structure) {
-        String trimmedStructure = structure
-            .replace(" ", "")
-            .replace("\n", "");
-        
-        if (trimmedStructure.length() != width * height)
-            throw new IllegalArgumentException("Structure size does not match GUI size");
-        
-        this.structure = trimmedStructure;
+    public GUIBuilder setStructure(@NotNull String structureData) {
+        this.structure = new Structure(structureData);
         return this;
     }
     
-    public GUIBuilder setIngredient(char key, @NotNull ItemBuilder itemBuilder) {
-        return setIngredient(key, new SimpleItem(itemBuilder));
-    }
-    
-    public GUIBuilder setIngredient(char key, @NotNull Item item) {
-        return setIngredient(key, new ItemSlotElement(item));
-    }
-    
-    public GUIBuilder setIngredient(char key, @NotNull SlotElement element) {
-        ingredientMap.put(key, new Ingredient(element));
+    public GUIBuilder setStructure(@NotNull Structure structure) {
+        this.structure = structure;
         return this;
     }
     
-    public GUIBuilder setMarker(char key, @NotNull Marker marker) {
-        ingredientMap.put(key, new Ingredient(marker));
+    public GUIBuilder addIngredient(char key, @NotNull ItemBuilder itemBuilder) {
+        structure.addIngredient(key, itemBuilder);
+        return this;
+    }
+    
+    public GUIBuilder addIngredient(char key, @NotNull Item item) {
+        structure.addIngredient(key, item);
+        return this;
+    }
+    
+    public GUIBuilder addIngredient(char key, @NotNull SlotElement element) {
+        structure.addIngredient(key, element);
+        return this;
+    }
+    
+    public GUIBuilder addIngredient(char key, @NotNull Marker marker) {
+        structure.addIngredient(key, marker);
+        return this;
+    }
+    
+    public GUIBuilder addIngredient(char key, @NotNull Supplier<Item> itemSupplier) {
+        structure.addIngredient(key, itemSupplier);
         return this;
     }
     
@@ -98,63 +102,46 @@ public class GUIBuilder {
     }
     
     public GUI build() {
-        IngredientList ingredients = new IngredientList(structure, ingredientMap);
-        
         switch (guiType) {
             
             case NORMAL:
-                return buildSimpleGUI(ingredients);
+                return buildSimpleGUI();
             
             case PAGED_ITEMS:
-                return buildSimplePagedItemsGUI(ingredients);
+                return buildSimplePagedItemsGUI();
             
             case PAGED_GUIs:
-                return buildSimplePagedGUIsGUI(ingredients);
+                return buildSimplePagedGUIsGUI();
             
             case TAB:
-                return buildSimpleTabGUI(ingredients);
+                return buildSimpleTabGUI();
             
             case SCROLL:
-                return buildSimpleScrollGUI(ingredients);
+                return buildSimpleScrollGUI();
             
             default:
                 throw new UnsupportedOperationException("Unknown GUI type");
         }
     }
     
-    private SimpleGUI buildSimpleGUI(IngredientList ingredients) {
-        SimpleGUI gui = new SimpleGUI(width, height);
-        ingredients.insertIntoGUI(gui);
-        
-        return gui;
+    private SimpleGUI buildSimpleGUI() {
+        return new SimpleGUI(width, height, structure);
     }
     
-    private SimplePagedItemsGUI buildSimplePagedItemsGUI(IngredientList ingredients) {
-        SimplePagedItemsGUI gui = new SimplePagedItemsGUI(width, height, items, ingredients.findIndicesOfMarkerAsArray(Marker.ITEM_LIST_SLOT));
-        ingredients.insertIntoGUI(gui);
-        
-        return gui;
+    private SimplePagedItemsGUI buildSimplePagedItemsGUI() {
+        return new SimplePagedItemsGUI(width, height, items, structure);
     }
     
-    private SimplePagedGUIsGUI buildSimplePagedGUIsGUI(IngredientList ingredients) {
-        SimplePagedGUIsGUI gui = new SimplePagedGUIsGUI(width, height, guis, ingredients.findIndicesOfMarkerAsArray(Marker.ITEM_LIST_SLOT));
-        ingredients.insertIntoGUI(gui);
-    
-        return gui;
+    private SimplePagedGUIsGUI buildSimplePagedGUIsGUI() {
+        return new SimplePagedGUIsGUI(width, height, guis, structure);
     }
     
-    private SimpleTabGUI buildSimpleTabGUI(IngredientList ingredients) {
-        SimpleTabGUI gui = new SimpleTabGUI(width, height, guis, ingredients.findIndicesOfMarkerAsArray(Marker.ITEM_LIST_SLOT));
-        ingredients.insertIntoGUI(gui);
-        
-        return gui;
+    private SimpleTabGUI buildSimpleTabGUI() {
+        return new SimpleTabGUI(width, height, guis, structure);
     }
     
-    private SimpleScrollGUI buildSimpleScrollGUI(IngredientList ingredients) {
-        SimpleScrollGUI gui = new SimpleScrollGUI(width, height, items, ingredients.findIndicesOfMarkerAsArray(Marker.ITEM_LIST_SLOT));
-        ingredients.insertIntoGUI(gui);
-        
-        return gui;
+    private SimpleScrollGUI buildSimpleScrollGUI() {
+        return new SimpleScrollGUI(width, height, items, structure);
     }
     
 }
diff --git a/src/main/java/de/studiocode/invui/gui/impl/IndexedGUI.java b/src/main/java/de/studiocode/invui/gui/impl/IndexedGUI.java
index 1f99b8b..af9bb95 100644
--- a/src/main/java/de/studiocode/invui/gui/impl/IndexedGUI.java
+++ b/src/main/java/de/studiocode/invui/gui/impl/IndexedGUI.java
@@ -8,6 +8,7 @@ import de.studiocode.invui.gui.SlotElement.ItemSlotElement;
 import de.studiocode.invui.gui.SlotElement.ItemStackHolder;
 import de.studiocode.invui.gui.SlotElement.LinkedSlotElement;
 import de.studiocode.invui.gui.SlotElement.VISlotElement;
+import de.studiocode.invui.gui.structure.Structure;
 import de.studiocode.invui.item.Item;
 import de.studiocode.invui.util.ArrayUtils;
 import de.studiocode.invui.virtualinventory.VirtualInventory;
@@ -375,6 +376,11 @@ abstract class IndexedGUI implements GUI {
         setSlotElement(index, null);
     }
     
+    @Override
+    public void applyStructure(Structure structure) {
+        structure.createIngredientList().insertIntoGUI(this);
+    }
+    
     @Override
     public int getSize() {
         return size;
diff --git a/src/main/java/de/studiocode/invui/gui/impl/PagedGUI.java b/src/main/java/de/studiocode/invui/gui/impl/PagedGUI.java
index aa592a4..0f03f56 100644
--- a/src/main/java/de/studiocode/invui/gui/impl/PagedGUI.java
+++ b/src/main/java/de/studiocode/invui/gui/impl/PagedGUI.java
@@ -4,6 +4,8 @@ import de.studiocode.invui.gui.Controllable;
 import de.studiocode.invui.gui.GUI;
 import de.studiocode.invui.gui.SlotElement;
 import de.studiocode.invui.gui.builder.GUIBuilder;
+import de.studiocode.invui.gui.structure.Marker;
+import de.studiocode.invui.gui.structure.Structure;
 import de.studiocode.invui.item.Item;
 import de.studiocode.invui.item.impl.controlitem.ControlItem;
 import de.studiocode.invui.item.impl.controlitem.PageItem;
@@ -31,6 +33,11 @@ public abstract class PagedGUI extends BaseGUI implements Controllable {
         this.itemListSlots = itemListSlots;
     }
     
+    public PagedGUI(int width, int height, boolean infinitePages, Structure structure) {
+        this(width, height, infinitePages, structure.createIngredientList().findIndicesOfMarker(Marker.ITEM_LIST_SLOT));
+        applyStructure(structure);
+    }
+    
     @Override
     public void addControlItem(int index, ControlItem<?> controlItem) {
         if (!(controlItem instanceof PageItem))
diff --git a/src/main/java/de/studiocode/invui/gui/impl/ScrollGUI.java b/src/main/java/de/studiocode/invui/gui/impl/ScrollGUI.java
index 9710b94..603c224 100644
--- a/src/main/java/de/studiocode/invui/gui/impl/ScrollGUI.java
+++ b/src/main/java/de/studiocode/invui/gui/impl/ScrollGUI.java
@@ -3,6 +3,8 @@ package de.studiocode.invui.gui.impl;
 import de.studiocode.invui.gui.Controllable;
 import de.studiocode.invui.gui.GUI;
 import de.studiocode.invui.gui.SlotElement;
+import de.studiocode.invui.gui.structure.Marker;
+import de.studiocode.invui.gui.structure.Structure;
 import de.studiocode.invui.item.Item;
 import de.studiocode.invui.item.impl.controlitem.ControlItem;
 import de.studiocode.invui.item.impl.controlitem.ScrollItem;
@@ -39,6 +41,11 @@ public abstract class ScrollGUI extends BaseGUI implements Controllable {
             throw new IllegalArgumentException("itemListSlots has to be a multiple of lineLength");
     }
     
+    public ScrollGUI(int width, int height, boolean infiniteLines, Structure structure) {
+        this(width, height, infiniteLines, structure.createIngredientList().findIndicesOfMarker(Marker.ITEM_LIST_SLOT));
+        applyStructure(structure);
+    }
+    
     @Override
     public void addControlItem(int index, ControlItem<?> controlItem) {
         if (!(controlItem instanceof ScrollItem))
diff --git a/src/main/java/de/studiocode/invui/gui/impl/SimpleGUI.java b/src/main/java/de/studiocode/invui/gui/impl/SimpleGUI.java
index 28a348b..60a775b 100644
--- a/src/main/java/de/studiocode/invui/gui/impl/SimpleGUI.java
+++ b/src/main/java/de/studiocode/invui/gui/impl/SimpleGUI.java
@@ -1,6 +1,8 @@
 package de.studiocode.invui.gui.impl;
 
 import de.studiocode.invui.gui.GUI;
+import de.studiocode.invui.gui.structure.Structure;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * A normal {@link GUI} without any special features.
@@ -11,4 +13,9 @@ public class SimpleGUI extends BaseGUI {
         super(width, height);
     }
     
+    public SimpleGUI(int width, int height, @NotNull Structure structure) {
+        super(width, height);
+        applyStructure(structure);
+    }
+    
 }
diff --git a/src/main/java/de/studiocode/invui/gui/impl/SimplePagedGUIsGUI.java b/src/main/java/de/studiocode/invui/gui/impl/SimplePagedGUIsGUI.java
index dbfee62..f016aa6 100644
--- a/src/main/java/de/studiocode/invui/gui/impl/SimplePagedGUIsGUI.java
+++ b/src/main/java/de/studiocode/invui/gui/impl/SimplePagedGUIsGUI.java
@@ -3,6 +3,9 @@ package de.studiocode.invui.gui.impl;
 import de.studiocode.invui.gui.GUI;
 import de.studiocode.invui.gui.SlotElement;
 import de.studiocode.invui.gui.builder.GUIBuilder;
+import de.studiocode.invui.gui.structure.Structure;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -18,13 +21,16 @@ public class SimplePagedGUIsGUI extends PagedGUI {
     
     private List<GUI> guis;
     
-    public SimplePagedGUIsGUI(int width, int height, int... itemListSlots) {
-        this(width, height, new ArrayList<>(), itemListSlots);
+    public SimplePagedGUIsGUI(int width, int height, @Nullable List<GUI> guis, int... itemListSlots) {
+        super(width, height, false, itemListSlots);
+        this.guis = guis == null ? new ArrayList<>() : guis;
+        
+        update();
     }
     
-    public SimplePagedGUIsGUI(int width, int height, List<GUI> guis, int... itemListSlots) {
-        super(width, height, false, itemListSlots);
-        this.guis = guis;
+    public SimplePagedGUIsGUI(int width, int height, @Nullable List<GUI> guis, @NotNull Structure structure) {
+        super(width, height, false, structure);
+        this.guis = guis == null ? new ArrayList<>() : guis;
         
         update();
     }
diff --git a/src/main/java/de/studiocode/invui/gui/impl/SimplePagedItemsGUI.java b/src/main/java/de/studiocode/invui/gui/impl/SimplePagedItemsGUI.java
index 90a823f..d19aa5f 100644
--- a/src/main/java/de/studiocode/invui/gui/impl/SimplePagedItemsGUI.java
+++ b/src/main/java/de/studiocode/invui/gui/impl/SimplePagedItemsGUI.java
@@ -3,7 +3,10 @@ package de.studiocode.invui.gui.impl;
 import de.studiocode.invui.gui.SlotElement;
 import de.studiocode.invui.gui.SlotElement.ItemSlotElement;
 import de.studiocode.invui.gui.builder.GUIBuilder;
+import de.studiocode.invui.gui.structure.Structure;
 import de.studiocode.invui.item.Item;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -19,13 +22,16 @@ public class SimplePagedItemsGUI extends PagedGUI {
     
     private List<Item> items;
     
-    public SimplePagedItemsGUI(int width, int height, int... itemListSlots) {
-        this(width, height, new ArrayList<>(), itemListSlots);
+    public SimplePagedItemsGUI(int width, int height, @Nullable List<Item> items, int... itemListSlots) {
+        super(width, height, false, itemListSlots);
+        this.items = items == null ? new ArrayList<>() : items;
+        
+        update();
     }
     
-    public SimplePagedItemsGUI(int width, int height, List<Item> items, int... itemListSlots) {
-        super(width, height, false, itemListSlots);
-        this.items = items;
+    public SimplePagedItemsGUI(int width, int height, @Nullable List<Item> items, @NotNull Structure structure) {
+        super(width, height, false, structure);
+        this.items = items == null ? new ArrayList<>() : items;
         
         update();
     }
diff --git a/src/main/java/de/studiocode/invui/gui/impl/SimpleScrollGUI.java b/src/main/java/de/studiocode/invui/gui/impl/SimpleScrollGUI.java
index bc931a2..116c022 100644
--- a/src/main/java/de/studiocode/invui/gui/impl/SimpleScrollGUI.java
+++ b/src/main/java/de/studiocode/invui/gui/impl/SimpleScrollGUI.java
@@ -1,8 +1,12 @@
 package de.studiocode.invui.gui.impl;
 
 import de.studiocode.invui.gui.SlotElement;
+import de.studiocode.invui.gui.structure.Structure;
 import de.studiocode.invui.item.Item;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
+import java.util.ArrayList;
 import java.util.List;
 import java.util.stream.Collectors;
 
@@ -10,9 +14,16 @@ public class SimpleScrollGUI extends ScrollGUI {
     
     private List<Item> items;
     
-    public SimpleScrollGUI(int width, int height, List<Item> items, int... itemListSlots) {
+    public SimpleScrollGUI(int width, int height, @Nullable List<Item> items, int... itemListSlots) {
         super(width, height, false, itemListSlots);
-        this.items = items;
+        this.items = items == null ? new ArrayList<>() : items;
+        
+        update();
+    }
+    
+    public SimpleScrollGUI(int width, int height, @Nullable List<Item> items, @NotNull Structure structure) {
+        super(width, height, false, structure);
+        this.items = items == null ? new ArrayList<>() : items;
         
         update();
     }
diff --git a/src/main/java/de/studiocode/invui/gui/impl/SimpleTabGUI.java b/src/main/java/de/studiocode/invui/gui/impl/SimpleTabGUI.java
index 4a02f96..75ae857 100644
--- a/src/main/java/de/studiocode/invui/gui/impl/SimpleTabGUI.java
+++ b/src/main/java/de/studiocode/invui/gui/impl/SimpleTabGUI.java
@@ -3,6 +3,8 @@ package de.studiocode.invui.gui.impl;
 import de.studiocode.invui.gui.GUI;
 import de.studiocode.invui.gui.SlotElement;
 import de.studiocode.invui.gui.builder.GUIBuilder;
+import de.studiocode.invui.gui.structure.Structure;
+import org.jetbrains.annotations.NotNull;
 
 import java.util.Arrays;
 import java.util.List;
@@ -16,13 +18,20 @@ public class SimpleTabGUI extends TabGUI {
     
     private final List<GUI> tabs;
     
-    public SimpleTabGUI(int width, int height, List<GUI> tabs, int[] listSlots) {
+    public SimpleTabGUI(int width, int height, @NotNull List<GUI> tabs, int[] listSlots) {
         super(width, height, tabs.size(), listSlots);
         this.tabs = tabs;
         
         update();
     }
     
+    public SimpleTabGUI(int width, int height, @NotNull List<GUI> tabs, @NotNull Structure structure) {
+        super(width, height, tabs.size(), structure);
+        this.tabs = tabs;
+        
+        update();
+    }
+    
     @Override
     public List<SlotElement> getSlotElements(int tab) {
         return Arrays.asList(tabs.get(tab).getSlotElements());
diff --git a/src/main/java/de/studiocode/invui/gui/impl/TabGUI.java b/src/main/java/de/studiocode/invui/gui/impl/TabGUI.java
index ffbd612..ce6f4d2 100644
--- a/src/main/java/de/studiocode/invui/gui/impl/TabGUI.java
+++ b/src/main/java/de/studiocode/invui/gui/impl/TabGUI.java
@@ -2,6 +2,8 @@ package de.studiocode.invui.gui.impl;
 
 import de.studiocode.invui.gui.Controllable;
 import de.studiocode.invui.gui.SlotElement;
+import de.studiocode.invui.gui.structure.Marker;
+import de.studiocode.invui.gui.structure.Structure;
 import de.studiocode.invui.item.Item;
 import de.studiocode.invui.item.impl.controlitem.ControlItem;
 import de.studiocode.invui.item.impl.controlitem.TabItem;
@@ -23,6 +25,11 @@ public abstract class TabGUI extends BaseGUI implements Controllable {
         this.listSlots = listSlots;
     }
     
+    public TabGUI(int width, int height, int tabAmount, Structure structure) {
+        this(width, height, tabAmount, structure.createIngredientList().findIndicesOfMarker(Marker.ITEM_LIST_SLOT));
+        applyStructure(structure);
+    }
+    
     public void showTab(int tab) {
         if (tab < 0 || tab >= tabAmount)
             throw new IllegalArgumentException("Tab out of bounds");
diff --git a/src/main/java/de/studiocode/invui/gui/builder/Ingredient.java b/src/main/java/de/studiocode/invui/gui/structure/Ingredient.java
similarity index 50%
rename from src/main/java/de/studiocode/invui/gui/builder/Ingredient.java
rename to src/main/java/de/studiocode/invui/gui/structure/Ingredient.java
index e2f06e2..330e26d 100644
--- a/src/main/java/de/studiocode/invui/gui/builder/Ingredient.java
+++ b/src/main/java/de/studiocode/invui/gui/structure/Ingredient.java
@@ -1,57 +1,49 @@
-package de.studiocode.invui.gui.builder;
+package de.studiocode.invui.gui.structure;
 
-import de.studiocode.invui.gui.GUI;
 import de.studiocode.invui.gui.SlotElement;
-import de.studiocode.invui.item.itembuilder.ItemBuilder;
+import de.studiocode.invui.gui.SlotElement.ItemSlotElement;
+import de.studiocode.invui.item.Item;
 
-import java.util.function.Function;
+import java.util.function.Supplier;
 
 class Ingredient {
     
     private final SlotElement slotElement;
     private final Marker marker;
-    private final Function<GUI, ItemBuilder> builderFunction;
+    private final Supplier<Item> itemSupplier;
     
     public Ingredient(SlotElement slotElement) {
         this.slotElement = slotElement;
-        this.builderFunction = null;
+        this.itemSupplier = null;
+        this.marker = null;
+    }
+    
+    public Ingredient(Supplier<Item> itemSupplier) {
+        this.itemSupplier = itemSupplier;
+        this.slotElement = null;
         this.marker = null;
     }
     
     public Ingredient(Marker marker) {
         this.marker = marker;
         this.slotElement = null;
-        this.builderFunction = null;
-    }
-    
-    public Ingredient(Function<GUI, ItemBuilder> builderFunction) {
-        this.builderFunction = builderFunction;
-        this.slotElement = null;
-        this.marker = null;
+        this.itemSupplier = null;
     }
     
     public SlotElement getSlotElement() {
-        return slotElement;
+        return slotElement == null ? new ItemSlotElement(itemSupplier.get()) : slotElement;
     }
     
     public Marker getMarker() {
         return marker;
     }
     
-    public Function<GUI, ItemBuilder> getBuilderFunction() {
-        return builderFunction;
-    }
-    
     public boolean isSlotElement() {
-        return slotElement != null;
+        return slotElement != null || itemSupplier != null;
     }
     
     public boolean isMarker() {
         return marker != null;
     }
     
-    public boolean isBuilderFunction() {
-        return builderFunction != null;
-    }
-    
 }
\ No newline at end of file
diff --git a/src/main/java/de/studiocode/invui/gui/builder/IngredientList.java b/src/main/java/de/studiocode/invui/gui/structure/IngredientList.java
similarity index 82%
rename from src/main/java/de/studiocode/invui/gui/builder/IngredientList.java
rename to src/main/java/de/studiocode/invui/gui/structure/IngredientList.java
index 86d79ce..b79f7d8 100644
--- a/src/main/java/de/studiocode/invui/gui/builder/IngredientList.java
+++ b/src/main/java/de/studiocode/invui/gui/structure/IngredientList.java
@@ -1,4 +1,4 @@
-package de.studiocode.invui.gui.builder;
+package de.studiocode.invui.gui.structure;
 
 import de.studiocode.invui.gui.Controllable;
 import de.studiocode.invui.gui.GUI;
@@ -11,7 +11,7 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 
-class IngredientList extends ArrayList<Ingredient> {
+public class IngredientList extends ArrayList<Ingredient> {
     
     public IngredientList(String structure, HashMap<Character, Ingredient> ingredientMap) {
         for (char c : structure.toCharArray()) {
@@ -22,6 +22,9 @@ class IngredientList extends ArrayList<Ingredient> {
     }
     
     public void insertIntoGUI(GUI gui) {
+        if (size() != gui.getSize())
+            throw new IllegalArgumentException("Structure size does not match GUI size");
+        
         for (int i = 0; i < size(); i++) {
             Ingredient ingredient = get(i);
             if (ingredient != null && ingredient.isSlotElement()) {
@@ -40,7 +43,7 @@ class IngredientList extends ArrayList<Ingredient> {
         }
     }
     
-    public List<Integer> findIndicesOfMarker(Marker marker) {
+    public int[] findIndicesOfMarker(Marker marker) {
         List<Integer> indices = new ArrayList<>();
         for (int i = 0; i < size(); i++) {
             Ingredient ingredient = get(i);
@@ -48,11 +51,7 @@ class IngredientList extends ArrayList<Ingredient> {
                 indices.add(i);
         }
         
-        return indices;
-    }
-    
-    public int[] findIndicesOfMarkerAsArray(Marker marker) {
-        return findIndicesOfMarker(marker).stream().mapToInt(Integer::intValue).toArray();
+        return indices.stream().mapToInt(Integer::intValue).toArray();
     }
     
 }
diff --git a/src/main/java/de/studiocode/invui/gui/builder/Marker.java b/src/main/java/de/studiocode/invui/gui/structure/Marker.java
similarity index 55%
rename from src/main/java/de/studiocode/invui/gui/builder/Marker.java
rename to src/main/java/de/studiocode/invui/gui/structure/Marker.java
index 162bfc7..d8d4419 100644
--- a/src/main/java/de/studiocode/invui/gui/builder/Marker.java
+++ b/src/main/java/de/studiocode/invui/gui/structure/Marker.java
@@ -1,4 +1,4 @@
-package de.studiocode.invui.gui.builder;
+package de.studiocode.invui.gui.structure;
 
 public enum Marker {
     
diff --git a/src/main/java/de/studiocode/invui/gui/structure/Structure.java b/src/main/java/de/studiocode/invui/gui/structure/Structure.java
new file mode 100644
index 0000000..c49009b
--- /dev/null
+++ b/src/main/java/de/studiocode/invui/gui/structure/Structure.java
@@ -0,0 +1,82 @@
+package de.studiocode.invui.gui.structure;
+
+import de.studiocode.invui.gui.GUI;
+import de.studiocode.invui.gui.SlotElement;
+import de.studiocode.invui.gui.SlotElement.ItemSlotElement;
+import de.studiocode.invui.item.Item;
+import de.studiocode.invui.item.impl.SimpleItem;
+import de.studiocode.invui.item.itembuilder.ItemBuilder;
+import org.bukkit.inventory.ShapedRecipe;
+import org.jetbrains.annotations.NotNull;
+
+import java.util.HashMap;
+import java.util.function.Supplier;
+
+/**
+ * Provides an easy way to design {@link GUI}s.
+ * Inspired by Bukkit's {@link ShapedRecipe}, this class will let you
+ * design a {@link GUI} in a similar way.
+ */
+public class Structure {
+    
+    private static final HashMap<Character, Ingredient> globalIngredientMap = new HashMap<>();
+    
+    private final HashMap<Character, Ingredient> ingredientMap = new HashMap<>();
+    private final String structureData;
+    
+    public Structure(String structureData) {
+        this.structureData = structureData
+            .replace(" ", "")
+            .replace("\n", "");
+    }
+    
+    public static void addGlobalIngredient(char key, @NotNull ItemBuilder itemBuilder) {
+        addGlobalIngredient(key, new SimpleItem(itemBuilder));
+    }
+    
+    public static void addGlobalIngredient(char key, @NotNull Item item) {
+        addGlobalIngredient(key, new ItemSlotElement(item));
+    }
+    
+    public static void addGlobalIngredient(char key, @NotNull SlotElement element) {
+        globalIngredientMap.put(key, new Ingredient(element));
+    }
+    
+    public static void addGlobalIngredient(char key, @NotNull Marker marker) {
+        globalIngredientMap.put(key, new Ingredient(marker));
+    }
+    
+    public static void addGlobalIngredient(char key, @NotNull Supplier<Item> itemSupplier) {
+        globalIngredientMap.put(key, new Ingredient(itemSupplier));
+    }
+    
+    public Structure addIngredient(char key, @NotNull ItemBuilder itemBuilder) {
+        return addIngredient(key, new SimpleItem(itemBuilder));
+    }
+    
+    public Structure addIngredient(char key, @NotNull Item item) {
+        return addIngredient(key, new ItemSlotElement(item));
+    }
+    
+    public Structure addIngredient(char key, @NotNull SlotElement element) {
+        ingredientMap.put(key, new Ingredient(element));
+        return this;
+    }
+    
+    public Structure addIngredient(char key, @NotNull Marker marker) {
+        ingredientMap.put(key, new Ingredient(marker));
+        return this;
+    }
+    
+    public Structure addIngredient(char key, @NotNull Supplier<Item> itemSupplier) {
+        ingredientMap.put(key, new Ingredient(itemSupplier));
+        return this;
+    }
+    
+    public IngredientList createIngredientList() {
+        HashMap<Character, Ingredient> ingredients = new HashMap<>(globalIngredientMap);
+        this.ingredientMap.forEach(ingredients::put);
+        return new IngredientList(structureData, ingredients);
+    }
+    
+}
diff --git a/src/main/java/de/studiocode/invui/item/impl/controlitem/ControlItem.java b/src/main/java/de/studiocode/invui/item/impl/controlitem/ControlItem.java
index 9b8ccad..ea15c37 100644
--- a/src/main/java/de/studiocode/invui/item/impl/controlitem/ControlItem.java
+++ b/src/main/java/de/studiocode/invui/item/impl/controlitem/ControlItem.java
@@ -25,6 +25,9 @@ public abstract class ControlItem<G extends GUI> extends BaseItem {
     }
     
     public void setGui(G gui) {
+        if (this.gui != null)
+            throw new IllegalStateException("The GUI is already set. (One ControlItem can't control multiple GUIs)");
+        
         this.gui = gui;
     }