diff --git a/MCTG/MCTGApp/Program.cs b/MCTG/MCTGApp/Program.cs
index 275a069..eb783ba 100644
--- a/MCTG/MCTGApp/Program.cs
+++ b/MCTG/MCTGApp/Program.cs
@@ -1,4 +1,40 @@
 // See https://aka.ms/new-console-template for more information
-using ;
 
-Console.WriteLine("Hello, World!");
+using Model;
+
+
+Console.WriteLine("Hello, World!\n");
+
+
+// TESTS:
+
+BaseItem r1 = new Recipe("A recipe...");
+
+r1.DisplayItem();
+r1.DisplayId();
+r1.DisplayDescription();
+
+Console.WriteLine();
+
+RecipeCollection rc = new RecipeCollection("A recipe collection...");
+for (uint i = 0; i < 10; i++)
+{
+    rc += new Recipe($"Recipe number {i} in the collection.");  // test overload + operator
+}
+
+try // test overload of [] operator
+{
+    rc[1003].DisplayItem();
+    rc[2003].DisplayItem(); // incorrect index
+}
+catch (ArgumentNullException)
+{
+    Console.Error.WriteLine("An index are incorrect!\n");
+}
+
+
+foreach (Recipe r in rc.Collection)
+{
+    r.DisplayId();
+    r.DisplayDescription();
+}
diff --git a/MCTG/MCTGLib/BaseItem.cs b/MCTG/MCTGLib/BaseItem.cs
new file mode 100644
index 0000000..36a653c
--- /dev/null
+++ b/MCTG/MCTGLib/BaseItem.cs
@@ -0,0 +1,56 @@
+
+using System;
+
+namespace Model
+{
+    /// <summary>
+    /// Define the base structure of any Items.<br/>
+    /// An Item can be identifed and have a short description. It can also be displayed.
+    /// </summary>
+    public abstract class BaseItem : IDisplayable
+    {
+        /// <summary>
+        /// The identifier of an Item.<br/>
+        /// The first number correspond to the typs of the Item.
+        /// </summary>
+        public uint Id { get; }
+
+        /// <summary>
+        /// A short description of the Item. Useful to know what this Item stand for.
+        /// </summary>
+        public string Description { get; set; }
+
+
+        protected BaseItem(uint id, string description = "")
+        {
+            Id = id;
+            Description = description;
+        }
+
+
+        public override string ToString()
+        {
+            return
+                $"[ Class -BaseItem- ]\n\n" +
+                $"\t.Id  -  {Id}\n" +
+                $"\t.Description  -  {Description}\n" +
+                $"______\n\n";
+        }
+
+        // IDisplayable Implementation
+        public void DisplayId()
+        {
+            Console.WriteLine($".Id  -  {Id}");
+        }
+
+        public void DisplayDescription()
+        {
+            Console.WriteLine($".Description  -  {Description}");
+        }
+
+        public void DisplayItem()
+        {
+            Console.WriteLine(this.ToString());
+        }
+    }
+}
diff --git a/MCTG/MCTGLib/IDisplayable.cs b/MCTG/MCTGLib/IDisplayable.cs
new file mode 100644
index 0000000..fed294c
--- /dev/null
+++ b/MCTG/MCTGLib/IDisplayable.cs
@@ -0,0 +1,23 @@
+namespace Model
+{
+    /// <summary>
+    /// Define an Item that can be displayed.
+    /// </summary>
+    interface IDisplayable
+    {
+        /// <summary>
+        /// Display the Id of the Item
+        /// </summary>
+        void DisplayId();
+
+        /// <summary>
+        /// Display the Description of the Item
+        /// </summary>
+        void DisplayDescription();
+
+        /// <summary>
+        /// Display the entire Item (Id, Description and other...)
+        /// </summary>
+        void DisplayItem();
+    }
+}
diff --git a/MCTG/MCTGLib/ItemCollection.cs b/MCTG/MCTGLib/ItemCollection.cs
deleted file mode 100644
index a3c7d4e..0000000
--- a/MCTG/MCTGLib/ItemCollection.cs
+++ /dev/null
@@ -1,7 +0,0 @@
-namespace Model
-{
-    public class ItemCollection
-    {
-
-    }
-}
\ No newline at end of file
diff --git a/MCTG/MCTGLib/Recipe.cs b/MCTG/MCTGLib/Recipe.cs
new file mode 100644
index 0000000..0e6611f
--- /dev/null
+++ b/MCTG/MCTGLib/Recipe.cs
@@ -0,0 +1,47 @@
+using System;
+using System.Collections.Generic;
+
+namespace Model
+{
+    /// <summary>
+    /// A Recipe is a description of step and maybe some techniques, with an ingredient list to make a meal.<br/>
+    /// It is instantiated with a new unique four digit id, where the first one is 1.
+    /// </summary>
+    public class Recipe : BaseItem
+    {
+        /// <summary>
+        /// This static atrribute stand for the creation of a new id. It is incremented each time a new Recipe is instantiated.
+        /// </summary>
+        public static uint idIterator = 0;
+
+        /// <summary>
+        /// The title of the recipe.
+        /// </summary>
+        public string Title { get; set; }
+
+        /// <summary>
+        /// All the details about the preparation of the meal.
+        /// </summary>
+        public string Preparation { get; set; }
+
+
+        public Recipe(string description = "", string title = "", string preparation = "")
+            : base(idIterator+1000, description)
+        {
+            if (idIterator == 1000) throw new OverflowException("id has reach the maximum value.");
+            Title = title;
+            Preparation = preparation;
+            idIterator++;
+        }
+
+
+        public override string ToString()
+        {
+            return
+                $"[ Class -Recipe- ]\n\n" +
+                $"\t.Id  -  {Id}\n" +
+                $"\t.Description  -  {Description}\n" +
+                $"______\n\n";
+        }
+    }
+}
diff --git a/MCTG/MCTGLib/RecipeCollection.cs b/MCTG/MCTGLib/RecipeCollection.cs
new file mode 100644
index 0000000..594ae91
--- /dev/null
+++ b/MCTG/MCTGLib/RecipeCollection.cs
@@ -0,0 +1,86 @@
+using System;
+using System.Collections.Generic;
+
+namespace Model
+{
+    /// <summary>
+    /// A Recipe collection is a group of recipe.<br/>
+    /// It is instantiated with a new unique four digit id, where the first one is 2.
+    /// </summary>
+    public class RecipeCollection : BaseItem
+    {
+        /// <summary>
+        /// This static atrribute stand for the creation of a new id. It is incremented each time a new RecipeCollection is instantiated.
+        /// </summary>
+        private static uint idIterator = 0;
+
+        /// <summary>
+        /// The main composent of a RecipeCollection. This contain the Recipes included in this collection.
+        /// </summary>
+        public List<Recipe> Collection { get; set; }
+
+
+        public RecipeCollection(string description = "", List<Recipe>? collection = null)
+            : base(idIterator + 2000, description)
+        {
+            if (idIterator == 1000) throw new OverflowException("id has reach the maximum value.");
+
+            if (collection == null)
+                Collection = new List<Recipe>();
+            else
+                Collection = collection;
+
+            idIterator++;
+        }
+
+
+        public override string ToString()
+        {
+            return
+                $"[ Class -RecipeCollection- ]\n\n" +
+                $"\t.Id  -  {Id}\n" +
+                $"\t.Description  -  {Description}\n" +
+                $"______\n\n";
+        }
+
+        /// <summary>
+        /// Overload the [] operator to access the Recipe directly without passing by the Collection.<br/>
+        /// It use the identifier of the Recipe to get the item.
+        /// </summary>
+        /// <param name="id">The id of the Recipe</param>
+        /// <returns></returns>
+        public Recipe this[uint id]
+        {
+            get
+            {
+                foreach (Recipe r in this.Collection)
+                {
+                    if (r.Id == id) return r;
+                }
+                throw new ArgumentNullException("The id given dosen't correspond to any recipes in the collection.");
+            }
+        }
+
+        /// <summary>
+        /// Overload of + operator to add a Recipe to a RecipeCollection.
+        /// </summary>
+        /// <param name="coll">The recipe collection where the recipe will be added</param>
+        /// <param name="ri">The recipe to add</param>
+        /// <returns>The recipe collection where the recipe is added.</returns>
+        public static RecipeCollection operator + (RecipeCollection coll, Recipe ri)
+        {
+            coll.Collection.Add(ri); return coll;
+        }
+
+        /// <summary>
+        /// Overload of - operator to remove a Recipe to a RecipeCollection.
+        /// </summary>
+        /// <param name="coll">The recipe collection where the recipe will be removed</param>
+        /// <param name="ri">The recipe to remove</param>
+        /// <returns>The recipe collection where the recipe is removed.</returns>
+        public static RecipeCollection operator - (RecipeCollection coll, Recipe ri)
+        {
+            coll.Collection.Remove(ri); return coll;
+        }
+    }
+}