diff --git a/src/Collection/ArrayCollection.php b/src/Collection/ArrayCollection.php
index b9171370..2285445a 100644
--- a/src/Collection/ArrayCollection.php
+++ b/src/Collection/ArrayCollection.php
@@ -21,8 +21,9 @@
 /**
  * @template E of IEntity
  * @implements ICollection<E>
+ * @implements MemoryCollection<E>
  */
-class ArrayCollection implements ICollection
+class ArrayCollection implements ICollection, MemoryCollection
 {
 	/**
 	 * @var callable[]
@@ -246,6 +247,12 @@ public function countStored(): int
 	}
 
 
+	public function toMemoryCollection(): MemoryCollection
+	{
+		return clone $this;
+	}
+
+
 	public function setRelationshipMapper(IRelationshipMapper $mapper = null, IEntity $parent = null): ICollection
 	{
 		$this->relationshipMapper = $mapper;
diff --git a/src/Collection/DbalCollection.php b/src/Collection/DbalCollection.php
index fc22ec24..6a6abf54 100644
--- a/src/Collection/DbalCollection.php
+++ b/src/Collection/DbalCollection.php
@@ -266,6 +266,14 @@ public function countStored(): int
 	}
 
 
+	public function toMemoryCollection(): MemoryCollection
+	{
+		$collection = clone $this;
+		$entities = $collection->fetchAll();
+		return new ArrayCollection($entities, $this->mapper->getRepository());
+	}
+
+
 	public function setRelationshipMapper(IRelationshipMapper $mapper = null, IEntity $parent = null): ICollection
 	{
 		$this->relationshipMapper = $mapper;
diff --git a/src/Collection/EmptyCollection.php b/src/Collection/EmptyCollection.php
index f40f9d7b..f5f2e042 100644
--- a/src/Collection/EmptyCollection.php
+++ b/src/Collection/EmptyCollection.php
@@ -13,8 +13,9 @@
 /**
  * @template E of IEntity
  * @implements ICollection<E>
+ * @implements MemoryCollection<E>
  */
-final class EmptyCollection implements ICollection
+final class EmptyCollection implements ICollection, MemoryCollection
 {
 	/** @var IRelationshipMapper|null */
 	private $relationshipMapper;
@@ -126,6 +127,12 @@ public function count(): int
 	}
 
 
+	public function toMemoryCollection(): MemoryCollection
+	{
+		return clone $this;
+	}
+
+
 	public function subscribeOnEntityFetch(callable $callback): void
 	{
 	}
diff --git a/src/Collection/HasManyCollection.php b/src/Collection/HasManyCollection.php
index e7cd658b..e5611d0c 100644
--- a/src/Collection/HasManyCollection.php
+++ b/src/Collection/HasManyCollection.php
@@ -30,6 +30,9 @@ class HasManyCollection implements ICollection
 	 */
 	public $onEntityFetch = [];
 
+	/** @var IRepository<E> */
+	private $repository;
+
 	/**
 	 * @var ICollection<IEntity>
 	 * @phpstan-var ICollection<E>
@@ -63,6 +66,7 @@ public function __construct(
 		callable $diffCallback
 	)
 	{
+		$this->repository = $repository;
 		$this->storageCollection = $innerCollection;
 		$this->diffCallback = $diffCallback;
 		$this->inMemoryCollection = new MutableArrayCollection([], $repository); // @phpstan-ignore-line
@@ -213,6 +217,14 @@ public function countStored(): int
 	}
 
 
+	public function toMemoryCollection(): MemoryCollection
+	{
+		$collection = clone $this;
+		$entities = $collection->fetchAll();
+		return new ArrayCollection($entities, $this->repository);
+	}
+
+
 	public function setRelationshipMapper(IRelationshipMapper $mapper = null): ICollection
 	{
 		$this->storageCollection->setRelationshipMapper($mapper);
diff --git a/src/Collection/ICollection.php b/src/Collection/ICollection.php
index c7066f12..adff093c 100644
--- a/src/Collection/ICollection.php
+++ b/src/Collection/ICollection.php
@@ -193,6 +193,13 @@ public function fetchPairs(?string $key = null, ?string $value = null): array;
 	public function getIterator();
 
 
+	/**
+	 * Fetches requested data and returns MemoryCollection instance with the fetched entities.
+	 * @return MemoryCollection<E>
+	 */
+	public function toMemoryCollection(): MemoryCollection;
+
+
 	/**
 	 * Sets relationship mapping over the collection.
 	 * @return static
diff --git a/src/Collection/MemoryCollection.php b/src/Collection/MemoryCollection.php
new file mode 100644
index 00000000..1ff9fe75
--- /dev/null
+++ b/src/Collection/MemoryCollection.php
@@ -0,0 +1,15 @@
+<?php declare(strict_types = 1);
+
+namespace Nextras\Orm\Collection;
+
+
+/**
+ * This kind of collection promises in-memory processing of data.
+ *
+ * @template E of \Nextras\Orm\Entity\IEntity
+ * @extends ICollection<E>
+ */
+interface MemoryCollection extends ICollection
+{
+}
+
diff --git a/src/Relationships/IRelationshipCollection.php b/src/Relationships/IRelationshipCollection.php
index bfccf920..2b3c9392 100644
--- a/src/Relationships/IRelationshipCollection.php
+++ b/src/Relationships/IRelationshipCollection.php
@@ -52,7 +52,7 @@ public function toCollection(): ICollection;
 
 
 	/**
-	 * Returns true if colletion was loaded.
+	 * Returns true if collection was loaded.
 	 */
 	public function isLoaded(): bool;
 
diff --git a/tests/cases/integration/Collection/collection.phpt b/tests/cases/integration/Collection/collection.phpt
index d6dad77b..19dbf1a1 100644
--- a/tests/cases/integration/Collection/collection.phpt
+++ b/tests/cases/integration/Collection/collection.phpt
@@ -8,8 +8,13 @@
 namespace NextrasTests\Orm\Integration\Collection;
 
 
+use Nextras\Orm\Collection\ArrayCollection;
+use Nextras\Orm\Collection\DbalCollection;
+use Nextras\Orm\Collection\EmptyCollection;
+use Nextras\Orm\Collection\HasManyCollection;
 use Nextras\Orm\Collection\ICollection;
 use Nextras\Orm\Exception\NoResultException;
+use NextrasTests\Orm\Author;
 use NextrasTests\Orm\Book;
 use NextrasTests\Orm\DataTestCase;
 use NextrasTests\Orm\Ean;
@@ -309,6 +314,40 @@ class CollectionTest extends DataTestCase
 		$books = $this->orm->tagFollowers->findBy(['tag->books->id' => 1]);
 		Assert::count(2, $books);
 	}
+
+
+	public function testToArrayCollection(): void
+	{
+		$c1 = $this->orm->authors->findAll();
+		$c2 = $c1->toMemoryCollection();
+		Assert::type(ArrayCollection::class, $c2);
+		Assert::same($c2->count(), $c1->countStored());
+
+		$author = $this->orm->authors->getByIdChecked(1);
+		$c3 = $author->books->toCollection();
+		$c4 = $c3->toMemoryCollection();
+		if ($this->section === Helper::SECTION_ARRAY) {
+			Assert::type(ArrayCollection::class, $c3);
+		} else {
+			Assert::type(DbalCollection::class, $c3);
+		}
+		Assert::type(ArrayCollection::class, $c4);
+		Assert::same($c4->count(), $c3->countStored());
+
+		$author->books->add(new Book());
+		$c5 = $author->books->toCollection();
+		$c6 = $c5->toMemoryCollection();
+		Assert::type(HasManyCollection::class, $c5);
+		Assert::type(ArrayCollection::class, $c6);
+		Assert::same($c6->count(), $c5->countStored());
+
+		$author = new Author();
+		$c7 = $author->tagFollowers->toCollection();
+		$c8 = $c7->toMemoryCollection();
+		Assert::type(EmptyCollection::class, $c7);
+		Assert::type(EmptyCollection::class, $c8);
+		Assert::same($c8->count(), $c7->countStored());
+	}
 }