diff --git a/src/Database/Concerns/BelongsToTenant.php b/src/Database/Concerns/BelongsToTenant.php
new file mode 100644
index 00000000..6c5b8224
--- /dev/null
+++ b/src/Database/Concerns/BelongsToTenant.php
@@ -0,0 +1,33 @@
+<?php
+
+namespace Stancl\Tenancy\Database\Concerns;
+
+use Stancl\Tenancy\Contracts\Tenant;
+use Stancl\Tenancy\Database\TenantScope;
+
+/**
+ * @property-read Tenant $tenant
+ */
+trait BelongsToTenant
+{
+    public static $tenantIdColumn = 'tenant_id';
+
+    public function tenant()
+    {
+        return $this->belongsTo(config('tenancy.tenant_model'), BelongsToTenant::$tenantIdColumn);
+    }
+
+    public static function bootBelongsToTenant()
+    {
+        static::addGlobalScope(new TenantScope(BelongsToTenant::$tenantIdColumn));
+
+        static::creating(function ($model) {
+            if (! $model->getAttribute(BelongsToTenant::$tenantIdColumn) && ! $model->relationLoaded('tenant')) {
+                if (tenancy()->initialized) {
+                    $model->setAttribute(BelongsToTenant::$tenantIdColumn, tenant()->getTenantKey());
+                    $model->setRelation('tenant', tenant());
+                }
+            }
+        });
+    }
+}
diff --git a/src/Database/Concerns/HasDomains.php b/src/Database/Concerns/HasDomains.php
index b8e70f09..7e5634a8 100644
--- a/src/Database/Concerns/HasDomains.php
+++ b/src/Database/Concerns/HasDomains.php
@@ -5,7 +5,7 @@ namespace Stancl\Tenancy\Database\Concerns;
 use Stancl\Tenancy\Contracts\Domain;
 
 /**
- * @property-read Domain[] $domains
+ * @property-read Domain[]\Illuminate\Database\Eloquent\Collection $domains
  */
 trait HasDomains
 {
diff --git a/src/Database/Models/Tenant.php b/src/Database/Models/Tenant.php
index 1ccebc23..761b4c07 100644
--- a/src/Database/Models/Tenant.php
+++ b/src/Database/Models/Tenant.php
@@ -6,7 +6,7 @@ use Carbon\Carbon;
 use Illuminate\Database\Eloquent\Model;
 use Stancl\Tenancy\Events;
 use Stancl\Tenancy\Contracts;
-use Stancl\Tenancy\Database\Collections\TenantCollection;
+use Stancl\Tenancy\Database\TenantCollection;
 use Stancl\Tenancy\Database\Concerns;
 
 /**
diff --git a/src/Database/Collections/TenantCollection.php b/src/Database/TenantCollection.php
similarity index 90%
rename from src/Database/Collections/TenantCollection.php
rename to src/Database/TenantCollection.php
index 298f0d25..689db690 100644
--- a/src/Database/Collections/TenantCollection.php
+++ b/src/Database/TenantCollection.php
@@ -1,6 +1,6 @@
 <?php
 
-namespace Stancl\Tenancy\Database\Collections;
+namespace Stancl\Tenancy\Database;
 
 use Illuminate\Database\Eloquent\Collection;
 use Stancl\Tenancy\Contracts\Tenant;
diff --git a/src/Database/TenantScope.php b/src/Database/TenantScope.php
new file mode 100644
index 00000000..d5ae7cda
--- /dev/null
+++ b/src/Database/TenantScope.php
@@ -0,0 +1,27 @@
+<?php
+
+namespace Stancl\Tenancy\Database;
+
+use Illuminate\Database\Eloquent\Builder;
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Scope;
+use Stancl\Tenancy\Database\Concerns\BelongsToTenant;
+
+class TenantScope implements Scope
+{
+    public function apply(Builder $builder, Model $model)
+    {
+        if (! tenancy()->initialized) {
+            return;
+        }
+
+        $builder->where(BelongsToTenant::$tenantIdColumn, tenant()->getTenantKey());
+    }
+
+    public function extend(Builder $builder)
+    {
+        $builder->macro('withoutTenancy', function (Builder $builder) {
+            return $builder->withoutGlobalScope($this);
+        });
+    }
+}
diff --git a/tests/SingleDatabaseTenancyTest.php b/tests/SingleDatabaseTenancyTest.php
new file mode 100644
index 00000000..1359c56a
--- /dev/null
+++ b/tests/SingleDatabaseTenancyTest.php
@@ -0,0 +1,272 @@
+<?php
+
+namespace Stancl\Tenancy\Tests;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\QueryException;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\DB;
+use Illuminate\Support\Facades\Schema;
+use Stancl\Tenancy\Database\Concerns\BelongsToTenant;
+use Stancl\Tenancy\Tests\Etc\Tenant;
+
+class SingleDatabaseTenancyTest extends TestCase
+{
+    public function setUp(): void
+    {
+        parent::setUp();
+
+        BelongsToTenant::$tenantIdColumn = 'tenant_id';
+
+        Schema::create('posts', function (Blueprint $table) {
+            $table->increments('id');
+            $table->string('text');
+
+            $table->string('tenant_id');
+
+            $table->foreign('tenant_id')->references('id')->on('tenants')->onUpdate('cascade')->onDelete('cascade');
+        });
+
+        Schema::create('comments', function (Blueprint $table) {
+            $table->increments('id');
+            $table->string('text');
+
+            $table->string('post_id');
+
+            $table->foreign('post_id')->references('id')->on('posts')->onUpdate('cascade')->onDelete('cascade');
+        });
+    }
+
+    /** @test */
+    public function primary_models_are_scoped_to_the_current_tenant()
+    {
+        // acme context
+        tenancy()->initialize($acme = Tenant::create([
+            'id' => 'acme',
+        ]));
+
+        $post = Post::create(['text' => 'Foo']);
+
+        $this->assertSame('acme', $post->tenant_id);
+        $this->assertSame('acme', $post->tenant->id);
+
+        $post = Post::first();
+
+        $this->assertSame('acme', $post->tenant_id);
+        $this->assertSame('acme', $post->tenant->id);
+
+        // ======================================
+        // foobar context
+        tenancy()->initialize($foobar = Tenant::create([
+            'id' => 'foobar',
+        ]));
+
+        $post = Post::create(['text' => 'Bar']);
+
+        $this->assertSame('foobar', $post->tenant_id);
+        $this->assertSame('foobar', $post->tenant->id);
+
+        $post = Post::first();
+
+        $this->assertSame('foobar', $post->tenant_id);
+        $this->assertSame('foobar', $post->tenant->id);
+
+        // ======================================
+        // acme context again
+
+        tenancy()->initialize($acme);
+
+        $post = Post::first();
+        $this->assertSame('acme', $post->tenant_id);
+        $this->assertSame('acme', $post->tenant->id);
+
+        // Assert foobar models are inaccessible in acme context
+        $this->assertSame(1, Post::count());
+    }
+
+    /** @test */
+    public function primary_models_are_not_scoped_in_the_central_context()
+    {
+        $this->primary_models_are_scoped_to_the_current_tenant();
+
+        tenancy()->end();
+
+        $this->assertSame(2, Post::count());
+    }
+
+    /** @test */
+    public function secondary_models_are_scoped_to_the_current_tenant_when_accessed_via_primary_model()
+    {
+        // acme context
+        tenancy()->initialize($acme = Tenant::create([
+            'id' => 'acme',
+        ]));
+
+        $post = Post::create(['text' => 'Foo']);
+        $post->comments()->create(['text' => 'Comment text']);
+
+        // ================
+        // foobar context
+        tenancy()->initialize($foobar = Tenant::create([
+            'id' => 'foobar',
+        ]));
+
+        $post = Post::create(['text' => 'Bar']);
+        $post->comments()->create(['text' => 'Comment text 2']);
+
+        // ================
+        // acme context again
+        tenancy()->initialize($acme);
+        $this->assertSame(1, Post::count());
+        $this->assertSame(1, Post::first()->comments->count());
+    }
+
+    /** @test */
+    public function secondary_models_are_NOT_scoped_to_the_current_tenant_when_accessed_directly()
+    {
+        $this->secondary_models_are_scoped_to_the_current_tenant_when_accessed_via_primary_model();
+
+        // We're in acme context
+        $this->assertSame('acme', tenant('id'));
+
+        // There is no way to scope this 🤷‍♂
+        $this->assertSame(2, Comment::count());
+    }
+
+    /** @test */
+    public function secondary_models_are_NOT_scoped_in_the_central_context()
+    {
+        $this->secondary_models_are_scoped_to_the_current_tenant_when_accessed_via_primary_model();
+
+        tenancy()->end();
+
+        $this->assertSame(2, Comment::count());
+    }
+
+    /** @test */
+    public function global_models_are_not_scoped_at_all()
+    {
+        Schema::create('global_resource', function (Blueprint $table) {
+            $table->increments('id');
+            $table->string('text');
+        });
+
+        GlobalResource::create(['text' => 'First']);
+        GlobalResource::create(['text' => 'Second']);
+
+        $acme = Tenant::create([
+            'id' => 'acme',
+        ]);
+
+        $acme->run(function () {
+            $this->assertSame(2, GlobalResource::count());
+
+            GlobalResource::create(['text' => 'Third']);
+            GlobalResource::create(['text' => 'Fourth']);
+        });
+
+        $this->assertSame(4, GlobalResource::count());
+    }
+
+    /** @test */
+    public function tenant_id_and_relationship_is_auto_added_when_creating_primary_resources_in_tenant_context()
+    {
+        tenancy()->initialize($acme = Tenant::create([
+            'id' => 'acme',
+        ]));
+
+        $post = Post::create(['text' => 'Foo']);
+
+        $this->assertSame('acme', $post->tenant_id);
+        $this->assertTrue($post->relationLoaded('tenant'));
+        $this->assertSame($acme, $post->tenant);
+        $this->assertSame(tenant(), $post->tenant);
+    }
+
+    /** @test */
+    public function tenant_id_is_not_auto_added_when_creating_primary_resources_in_central_context()
+    {
+        $this->expectException(QueryException::class);
+
+        Post::create(['text' => 'Foo']);
+    }
+
+    /** @test */
+    public function tenant_id_column_name_can_be_customized()
+    {
+        BelongsToTenant::$tenantIdColumn = 'team_id';
+
+        Schema::drop('posts');
+        Schema::create('posts', function (Blueprint $table) {
+            $table->increments('id');
+            $table->string('text');
+
+            $table->string('team_id');
+
+            $table->foreign('team_id')->references('id')->on('tenants')->onUpdate('cascade')->onDelete('cascade');
+        });
+
+        tenancy()->initialize($acme = Tenant::create([
+            'id' => 'acme',
+        ]));
+
+        $post = Post::create(['text' => 'Foo']);
+
+        $this->assertSame('acme', $post->team_id);
+
+        // ======================================
+        // foobar context
+        tenancy()->initialize($foobar = Tenant::create([
+            'id' => 'foobar',
+        ]));
+
+        $post = Post::create(['text' => 'Bar']);
+
+        $this->assertSame('foobar', $post->team_id);
+
+        $post = Post::first();
+
+        $this->assertSame('foobar', $post->team_id);
+
+        // ======================================
+        // acme context again
+
+        tenancy()->initialize($acme);
+
+        $post = Post::first();
+        $this->assertSame('acme', $post->team_id);
+
+        // Assert foobar models are inaccessible in acme context
+        $this->assertSame(1, Post::count());
+    }
+}
+
+class Post extends Model
+{
+    use BelongsToTenant;
+
+    protected $guarded = [];
+    public $timestamps = false;
+
+    public function comments()
+    {
+        return $this->hasMany(Comment::class);
+    }
+}
+
+class Comment extends Model
+{
+    protected $guarded = [];
+    public $timestamps = false;
+
+    public function post()
+    {
+        return $this->belongsTo(Post::class);
+    }
+}
+
+class GlobalResource extends Model
+{
+    protected $guarded = [];
+    public $timestamps = false;
+}
\ No newline at end of file