diff --git a/backend/tests/Feature/Element/EloquentElementRepositoryTest.php b/backend/tests/Feature/Element/EloquentElementRepositoryTest.php
index 76766c5..9cc6020 100644
--- a/backend/tests/Feature/Element/EloquentElementRepositoryTest.php
+++ b/backend/tests/Feature/Element/EloquentElementRepositoryTest.php
@@ -5,7 +5,10 @@ namespace Tests\Feature\Element;
 use App\Element\CreateElementDto;
 use App\Element\ElementRepository;
 use App\Set\CreateSetDto;
+use App\Set\CreateSetLevelDto;
 use App\Set\Set;
+use App\Set\SetLevel;
+use App\Set\SetLevelRepository;
 use App\Set\SetRepository;
 use App\Shared\ValueObject\EmailAddress;
 use App\User\CreateUserDto;
@@ -22,28 +25,26 @@ class EloquentElementRepositoryTest extends TestCase
     {
         $set = $this->createSet('Bible');
         $repository = app(ElementRepository::class);
+        $bookLevel = $this->createLevel($set, 'book');
+        $portionLevel = $this->createLevel($set, 'portion');
         $genesisBook = $repository->create(new CreateElementDto(
-            set: $set,
             name: 'Genesis',
-            kind: 'book',
+            level: $bookLevel,
             parentElement: null,
         ));
         $exodusBook = $repository->create(new CreateElementDto(
-            set: $set,
             name: 'Exodus',
-            kind: 'book',
+            level: $bookLevel,
             parentElement: null,
         ));
         $genesisPortion = $repository->create(new CreateElementDto(
-            set: $set,
             name: 'Genesis',
-            kind: 'portion',
+            level: $portionLevel,
             parentElement: $genesisBook,
         ));
         $noahPortion = $repository->create(new CreateElementDto(
-            set: $set,
             name: 'Noah',
-            kind: 'portion',
+            level: $portionLevel,
             parentElement: $genesisBook,
         ));
 
@@ -53,9 +54,8 @@ class EloquentElementRepositoryTest extends TestCase
         $this->assertSame(2, $noahPortion->getPosition());
         $this->assertDatabaseHas('elements', [
             'id' => $genesisPortion->getId(),
-            'set_id' => $set->getId(),
+            'set_level_id' => $portionLevel->getId(),
             'name' => 'Genesis',
-            'kind' => 'portion',
             'parent_element_id' => $genesisBook->getId(),
             'position' => 1,
         ]);
@@ -65,6 +65,10 @@ class EloquentElementRepositoryTest extends TestCase
         $this->assertNotNull($foundElement);
         $this->assertSame('Noah', $foundElement->getName());
         $this->assertSame('portion', $foundElement->getKind());
+        $this->assertSame(
+            $portionLevel->getId(),
+            $foundElement->getLevel()->getId(),
+        );
         $this->assertSame($set->getId(), $foundElement->getSet()->getId());
         $this->assertSame(
             $genesisBook->getId(),
@@ -77,10 +81,11 @@ class EloquentElementRepositoryTest extends TestCase
         $bible = $this->createSet('Bible');
         $course = $this->createSet('Course');
         $repository = app(ElementRepository::class);
+        $bookLevel = $this->createLevel($bible, 'book');
+        $moduleLevel = $this->createLevel($course, 'module');
         $book = $repository->create(new CreateElementDto(
-            set: $bible,
             name: 'Genesis',
-            kind: 'book',
+            level: $bookLevel,
             parentElement: null,
         ));
 
@@ -90,9 +95,51 @@ class EloquentElementRepositoryTest extends TestCase
         );
 
         $repository->create(new CreateElementDto(
-            set: $course,
             name: 'Invalid lesson',
-            kind: 'lesson',
+            level: $moduleLevel,
+            parentElement: $book,
+        ));
+    }
+
+    public function testItRejectsARootOutsideTheFirstLevel(): void
+    {
+        $set = $this->createSet('Bible');
+        $this->createLevel($set, 'book');
+        $portionLevel = $this->createLevel($set, 'portion');
+
+        $this->expectException(DomainException::class);
+        $this->expectExceptionMessage(
+            'root element must use the first set level',
+        );
+
+        app(ElementRepository::class)->create(new CreateElementDto(
+            name: 'Creation',
+            level: $portionLevel,
+            parentElement: null,
+        ));
+    }
+
+    public function testItRejectsAChildOutsideTheNextLevel(): void
+    {
+        $set = $this->createSet('Bible');
+        $bookLevel = $this->createLevel($set, 'book');
+        $this->createLevel($set, 'portion');
+        $chapterLevel = $this->createLevel($set, 'chapter');
+        $repository = app(ElementRepository::class);
+        $book = $repository->create(new CreateElementDto(
+            name: 'Genesis',
+            level: $bookLevel,
+            parentElement: null,
+        ));
+
+        $this->expectException(DomainException::class);
+        $this->expectExceptionMessage(
+            'child element must use the next set level',
+        );
+
+        $repository->create(new CreateElementDto(
+            name: 'Chapter 1',
+            level: $chapterLevel,
             parentElement: $book,
         ));
     }
@@ -102,40 +149,37 @@ class EloquentElementRepositoryTest extends TestCase
         $bible = $this->createSet('Bible');
         $course = $this->createSet('Course');
         $repository = app(ElementRepository::class);
+        $bookLevel = $this->createLevel($bible, 'book');
+        $portionLevel = $this->createLevel($bible, 'portion');
+        $moduleLevel = $this->createLevel($course, 'module');
         $genesisBook = $repository->create(new CreateElementDto(
-            set: $bible,
             name: 'Genesis',
-            kind: 'book',
+            level: $bookLevel,
             parentElement: null,
         ));
         $exodusBook = $repository->create(new CreateElementDto(
-            set: $bible,
             name: 'Exodus',
-            kind: 'book',
+            level: $bookLevel,
             parentElement: null,
         ));
         $repository->create(new CreateElementDto(
-            set: $course,
             name: 'Module 1',
-            kind: 'module',
+            level: $moduleLevel,
             parentElement: null,
         ));
         $repository->create(new CreateElementDto(
-            set: $bible,
             name: 'Genesis',
-            kind: 'portion',
+            level: $portionLevel,
             parentElement: $genesisBook,
         ));
         $repository->create(new CreateElementDto(
-            set: $bible,
             name: 'Noah',
-            kind: 'portion',
+            level: $portionLevel,
             parentElement: $genesisBook,
         ));
         $repository->create(new CreateElementDto(
-            set: $bible,
             name: 'Shemot',
-            kind: 'portion',
+            level: $portionLevel,
             parentElement: $exodusBook,
         ));
 
@@ -161,22 +205,22 @@ class EloquentElementRepositoryTest extends TestCase
         $bible = $this->createSet('Bible');
         $course = $this->createSet('Course');
         $repository = app(ElementRepository::class);
+        $bookLevel = $this->createLevel($bible, 'book');
+        $portionLevel = $this->createLevel($bible, 'portion');
+        $moduleLevel = $this->createLevel($course, 'module');
         $genesis = $repository->create(new CreateElementDto(
-            set: $bible,
             name: 'Genesis',
-            kind: 'book',
+            level: $bookLevel,
             parentElement: null,
         ));
         $repository->create(new CreateElementDto(
-            set: $bible,
             name: 'Creation',
-            kind: 'portion',
+            level: $portionLevel,
             parentElement: $genesis,
         ));
         $repository->create(new CreateElementDto(
-            set: $course,
             name: 'Foundations',
-            kind: 'module',
+            level: $moduleLevel,
             parentElement: null,
         ));
 
@@ -207,4 +251,12 @@ class EloquentElementRepositoryTest extends TestCase
             creator: $creator,
         ));
     }
+
+    private function createLevel(Set $set, string $kind): SetLevel
+    {
+        return app(SetLevelRepository::class)->create(new CreateSetLevelDto(
+            set: $set,
+            kind: $kind,
+        ));
+    }
 }
diff --git a/backend/tests/Unit/Element/ElementTest.php b/backend/tests/Unit/Element/ElementTest.php
index 1a99b31..3acd12d 100644
--- a/backend/tests/Unit/Element/ElementTest.php
+++ b/backend/tests/Unit/Element/ElementTest.php
@@ -4,6 +4,7 @@ namespace Tests\Unit\Element;
 
 use App\Element\Element;
 use App\Set\Set;
+use App\Set\SetLevel;
 use App\Shared\ValueObject\EmailAddress;
 use App\User\User;
 use PHPUnit\Framework\TestCase;
@@ -22,19 +23,29 @@ class ElementTest extends TestCase
             name: 'Bible',
             creator: $creator,
         );
+        $bookLevel = new SetLevel(
+            id: 31,
+            set: $set,
+            kind: 'book',
+            depth: 0,
+        );
+        $portionLevel = new SetLevel(
+            id: 32,
+            set: $set,
+            kind: 'portion',
+            depth: 1,
+        );
         $parentElement = new Element(
             id: 21,
             name: 'Genesis',
-            kind: 'book',
-            set: $set,
+            level: $bookLevel,
             parentElement: null,
             position: 1,
         );
         $element = new Element(
             id: 22,
             name: 'Genesis',
-            kind: 'portion',
-            set: $set,
+            level: $portionLevel,
             parentElement: $parentElement,
             position: 2,
         );
@@ -42,6 +53,7 @@ class ElementTest extends TestCase
         $this->assertSame(22, $element->getId());
         $this->assertSame('Genesis', $element->getName());
         $this->assertSame('portion', $element->getKind());
+        $this->assertSame($portionLevel, $element->getLevel());
         $this->assertSame($set, $element->getSet());
         $this->assertSame($parentElement, $element->getParentElement());
         $this->assertSame(2, $element->getPosition());