diff --git a/src/main/java/com/booleanuk/core/Account.java b/src/main/java/com/booleanuk/core/Account.java
new file mode 100644
index 0000000..8192fea
--- /dev/null
+++ b/src/main/java/com/booleanuk/core/Account.java
@@ -0,0 +1,34 @@
+package com.booleanuk.core;
+
+public class Account {
+    private String email;
+    private String password;
+    private boolean status;
+
+    public Account(String email, String password) throws Exception {
+        this.setEmail(email);
+        this.setPassword(password);
+        this.status = false;
+    }
+
+    public void setEmail(String email) throws Exception {
+        if (email.contains("@")){
+            this.email = email;
+        }
+
+        // TODO:
+        // Should return false if following domain model idea
+        // Or throw an error instead of just printing out to the console.
+//        System.out.println("ERROR: Email is not valid.");
+        this.email = null;
+        throw new Exception("ERROR: Email is not valid.");
+    }
+
+    public void setPassword(String password) {
+        this.password = password;
+    }
+
+    public void setStatus(boolean status) {
+        this.status = status;
+    }
+}
diff --git a/src/main/java/com/booleanuk/core/TodoItem.java b/src/main/java/com/booleanuk/core/TodoItem.java
index 655d825..3c0a15e 100644
--- a/src/main/java/com/booleanuk/core/TodoItem.java
+++ b/src/main/java/com/booleanuk/core/TodoItem.java
@@ -1,21 +1,29 @@
 package com.booleanuk.core;
 
 public class TodoItem {
-    public String title;
-    public String detail;
-    public String status;
+    private String title;
+    private String detail;
+    private String status;
 
-    public TodoItem(String title, String detail, String status) {
+    public TodoItem(String title, String detail) {
         this.title = title;
         this.detail = detail;
-        this.status = status;
+        this.status = "incomplete";
     }
 
-    public void setStatus(String status) {
+    private void setStatus(String status) {
         this.status = status;
     }
 
     public String getStatus() {
         return this.status;
     }
+
+    public void markAsComplete() {
+        this.setStatus("complete");
+    }
+
+    public void markAsIncomplete() {
+        this.setStatus("incomplete");
+    }
 }
diff --git a/src/main/java/com/booleanuk/core/domain-model.md b/src/main/java/com/booleanuk/core/domain-model.md
new file mode 100644
index 0000000..95d2b97
--- /dev/null
+++ b/src/main/java/com/booleanuk/core/domain-model.md
@@ -0,0 +1,11 @@
+| Classes                                  | Variables  | Methods                          | Scenario                              | Output               |
+|------------------------------------------|------------|----------------------------------|---------------------------------------|----------------------|
+| `Account(String email, String password)` | `email`    | `- setEmail(String email)`       | Valid email.                          | true                 |
+|                                          |            |                                  | Invalid email.                        | false, error message |
+|                                          | `password` | `- setPassword(String password)` | Valid password.                       | true                 |
+|                                          |            |                                  | Invalid password.                     | false, error message |
+|                                          | `status`   | `- setStatus(boolean status)`    | Change status to enabled or disabled. | -                    |
+|                                          |            | `+ enable()`                     | Set status to enabled.                | -                    |
+|                                          |            | `+ disable()`                    | Set status to enabled.                | -                    |
+|                                          |            | `+ login()`                      | Account is enabled.                   | true                 |
+|                                          |            |                                  | Account is enabled.                   | false                |
diff --git a/src/test/java/com/booleanuk/core/AccountTest.java b/src/test/java/com/booleanuk/core/AccountTest.java
new file mode 100644
index 0000000..d4689b6
--- /dev/null
+++ b/src/test/java/com/booleanuk/core/AccountTest.java
@@ -0,0 +1,15 @@
+package com.booleanuk.core;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class AccountTest {
+
+    @Test
+    public void checkValidEmail() throws Exception {
+        Account account = new Account("email", "password");
+
+//        Assertions.assertThrows(Exeption(), "ERROR: Email is not valid.");
+
+    }
+}
diff --git a/src/test/java/com/booleanuk/core/TodoItemTest.java b/src/test/java/com/booleanuk/core/TodoItemTest.java
index 095af82..65b0b28 100644
--- a/src/test/java/com/booleanuk/core/TodoItemTest.java
+++ b/src/test/java/com/booleanuk/core/TodoItemTest.java
@@ -5,4 +5,14 @@
 
 class TodoItemTest {
 
+    @Test
+    public void checkSetStatus() {
+        TodoItem todo = new TodoItem("Todo", "JUnit testing");
+
+        todo.markAsComplete();
+        Assertions.assertEquals("complete", todo.getStatus());
+
+        todo.markAsIncomplete();
+        Assertions.assertEquals("incomplete", todo.getStatus());
+    }
 }