diff --git a/MCTG/ConsoleApp/Program.cs b/MCTG/ConsoleApp/Program.cs
index ac6bfb0..4a2aedd 100644
--- a/MCTG/ConsoleApp/Program.cs
+++ b/MCTG/ConsoleApp/Program.cs
@@ -9,13 +9,24 @@ Console.WriteLine("Hello, World!\n\n");
 // TESTS:
 
 RecipeCollection rc = new RecipeCollection("Desserts",
-    new Recipe("Cookies", "Cookies au chocolats", null,
+    new Recipe("Cookies", null,
         new PreparationStep(1, "Faire cuire le truc."),
         new PreparationStep(2, "Elaboré un autre truc"),
         new PreparationStep(3, null)),
-    new Recipe(null, null, 99,
+    new Recipe(null, 99,
         new PreparationStep(1, null),
         new PreparationStep(1, null)),
     new Recipe());
 
 Console.WriteLine(rc.ToString());
+
+Console.WriteLine(rc.GetRecipeById(99).ToString());
+
+try
+{
+    Console.WriteLine(rc.GetRecipeById(23).ToString());
+}
+catch (ArgumentException e)
+{
+    Console.Error.WriteLine(e.Message);
+}
diff --git a/MCTG/Model/PreparationStep.cs b/MCTG/Model/PreparationStep.cs
index 6057273..1301dac 100644
--- a/MCTG/Model/PreparationStep.cs
+++ b/MCTG/Model/PreparationStep.cs
@@ -6,14 +6,25 @@ using System.Threading.Tasks;
 
 namespace Model
 {
-    public class PreparationStep
+    /// <summary>
+    /// Define a step of the preparation of a recipe.
+    /// </summary>
+    public class PreparationStep : IEquatable<PreparationStep>
     {
         #region Attributes
         private string? _description;
         #endregion
 
         #region Properties
+        /// <summary>
+        /// The order of this step in the preparation of the meal.
+        /// </summary>
         public int Order { get; init; }
+
+        /// <summary>
+        /// The description of the task the user need to do for this step of the preparation. <br/>
+        /// Set to "No description." when the value passed is null, empty or contain white spaces.
+        /// </summary>
         public string? Description
         {
             get => _description;
@@ -28,6 +39,11 @@ namespace Model
         #endregion
 
         #region Constructors
+        /// <summary>
+        /// Construct a new step of preparation.
+        /// </summary>
+        /// <param name="order">The number of the order in preparation</param>
+        /// <param name="description">The description of the task</param>
         public PreparationStep(int order, string? description)
         {
             Order = order;
@@ -36,6 +52,11 @@ namespace Model
         #endregion
 
         #region Methods
+        public bool Equals(PreparationStep? other)
+        {
+            return Order.Equals(other.Order) && Description.Equals(other.Description);
+        }
+
         public override string ToString()
         {
             return $"{Order}- {Description}";
diff --git a/MCTG/Model/Recipe.cs b/MCTG/Model/Recipe.cs
index e493212..b575c6a 100644
--- a/MCTG/Model/Recipe.cs
+++ b/MCTG/Model/Recipe.cs
@@ -5,7 +5,9 @@ using System.Text;
 
 namespace Model
 {
-
+    /// <summary>
+    /// Define a Recipe for the preparation of a meal.
+    /// </summary>
     public class Recipe : IEquatable<Recipe>
     {
         #region Attributes
@@ -15,7 +17,15 @@ namespace Model
         #endregion
 
         #region Properties
+        /// <summary>
+        /// The ID of the recipe - allows you to compare and/or get this item in an easier way.
+        /// </summary>
         public int Id { get; init; }
+
+        /// <summary>
+        /// The Title of the recipe. <br/>
+        /// Set to "No title." when the value passed is null, empty or contain white spaces.
+        /// </summary>
         public string? Title
         {
             get => _title;
@@ -27,28 +37,26 @@ namespace Model
                     _title = value;
             }
         }
-        public string? Description
-        {
-            get => _description;
-            set
-            {
-                if (string.IsNullOrWhiteSpace(value))
-                    _description = "No description.";
-                else
-                    _description = value;
-            }
-        }
+
+        /// <summary>
+        /// The steps of the preparation. See: <see cref="PreparationStep"/>.
+        /// </summary>
         public List<PreparationStep>? PreparationSteps { get; private set; }
         #endregion
 
         #region Constructors
-        public Recipe(string? title = null, string? description = null, int? id = null,
+        /// <summary>
+        /// Construct a new recipe.
+        /// </summary>
+        /// <param name="title">The title of the recipe</param>
+        /// <param name="id">The id of the recipe. If not given, get a new id.</param>
+        /// <param name="preparationSteps">The steps of the preparation of the meal</param>
+        public Recipe(string? title = null, int? id = null,
                       params PreparationStep[] preparationSteps)
         {
             if (id == null) Id = idCreator++;
             else Id = (int)id;
             Title = title;
-            Description = description;
             PreparationSteps = new List<PreparationStep>(preparationSteps);
         }
         #endregion
@@ -58,7 +66,7 @@ namespace Model
         {
             if (other == null) return false;
             if (other == this) return true;
-            return Title.Equals(other.Title) && Description.Equals(other.Description);
+            return Title.Equals(other.Title) && PreparationSteps.Equals(other.PreparationSteps);
         }
 
         public override int GetHashCode()
@@ -68,7 +76,7 @@ namespace Model
 
         public override string ToString()
         {
-            StringBuilder sb = new StringBuilder($"[Recipe] - {Title}: {Description}\n");
+            StringBuilder sb = new StringBuilder($"[Recipe n°{Id}] - {Title}\n");
             foreach (PreparationStep ps in PreparationSteps)
             {
                 sb.AppendFormat("\t* {0}\n", ps.ToString());
diff --git a/MCTG/Model/RecipeCollection.cs b/MCTG/Model/RecipeCollection.cs
index 283af8e..2de66d6 100644
--- a/MCTG/Model/RecipeCollection.cs
+++ b/MCTG/Model/RecipeCollection.cs
@@ -6,7 +6,10 @@ using System.Text;
 
 namespace Model
 {
-
+    /// <summary>
+    /// Define a collection of <see cref="Recipe"/>.
+    /// <br/>This class implement <see cref="IList"/> and <see cref="IEquatable{T}"/>.
+    /// </summary>
     public class RecipeCollection : IList<Recipe>, IEquatable<RecipeCollection>
     {
         #region Attributes
@@ -15,6 +18,10 @@ namespace Model
         #endregion
 
         #region Properties
+        /// <summary>
+        /// A short description of what this collection contain. <br/>
+        /// Set to "No description." when the value passed is null, empty or contain white spaces.
+        /// </summary>
         public string? Description
         {
             get => _description;
@@ -35,6 +42,11 @@ namespace Model
         #endregion
 
         #region Constructors
+        /// <summary>
+        /// Construct a new collection of recipes.
+        /// </summary>
+        /// <param name="description">A short description of what this list will contain</param>
+        /// <param name="recipes">Recipes to add in this new collection</param>
         public RecipeCollection(string? description = null, params Recipe[] recipes)
         {
             this.recipes = new List<Recipe>(recipes);
@@ -43,6 +55,19 @@ namespace Model
         #endregion
 
         #region Methods
+        /// <summary>
+        /// Find a recipe in this list by giving the id.
+        /// </summary>
+        /// <param name="id">The id of the list we are looking for</param>
+        /// <returns>The recipe of the id given</returns>
+        /// <exception cref="ArgumentException"/>
+        public Recipe? GetRecipeById(int id)
+        {
+            Recipe? recipe = recipes.Find(r => r.Id == id);
+            if (recipe == null) throw new ArgumentException("No recipes match the given id.");
+            return recipe;
+        }
+
         #region IList Methods
         public int IndexOf(Recipe item)
         {
diff --git a/MCTG/Tests/Model_UnitTests/Recipe_UT.cs b/MCTG/Tests/Model_UnitTests/Recipe_UT.cs
index e1d6720..205d6cd 100644
--- a/MCTG/Tests/Model_UnitTests/Recipe_UT.cs
+++ b/MCTG/Tests/Model_UnitTests/Recipe_UT.cs
@@ -9,25 +9,20 @@ namespace Model_UnitTests
         {
             Recipe r = new Recipe(id: 999); // id is given to avoid tests errors with the static atrribute 'idCreator'.
             Assert.NotNull(r.Title);
-            Assert.NotNull(r.Description);
         }
 
         [Theory]
-        [InlineData("Cookies", "Choco Cookies", 23, "Cookies", "Choco Cookies", 23)]
-        [InlineData("Cookies", "No description.", 1, "Cookies", "", 1)]
-        [InlineData("No title.", "Choco Cookies", 1, "", "Choco Cookies", 1)]
-        [InlineData("Cookies", "Choco Cookies", 0, "Cookies", "Choco Cookies", null)]
-        [InlineData("Cookies", "No description.", 1, "Cookies", null, 1)]
-        [InlineData("No title.", "Choco Cookies", 1, null, "Choco Cookies", 1)]
-        public void TestConstructor(string expectedTitle, string expectedDescription, int expectedId,
-                                    string title, string description, int? id)
+        [InlineData("Cookies", 23, "Cookies", 23)]
+        [InlineData("Cookies", 1, "Cookies", 1)]
+        [InlineData("No title.", 1, "", 1)]
+        [InlineData("Cookies", 0, "Cookies", null)]
+        [InlineData("No title.", 1, null, 1)]
+        public void TestConstructor(string expectedTitle, int expectedId, string title, int? id)
         {
-            Recipe r = new Recipe(title, description, id);
+            Recipe r = new Recipe(title, id);
             Assert.NotNull(r.Title);
-            Assert.NotNull(r.Description);
             Assert.Equal(expectedId, r.Id);
             Assert.Equal(expectedTitle, r.Title);
-            Assert.Equal(expectedDescription, r.Description);
         }
     }
 }