diff --git a/wp-includes/class-wp-block-list.php b/wp-includes/class-wp-block-list.php
new file mode 100644
index 0000000000..378faba578
--- /dev/null
+++ b/wp-includes/class-wp-block-list.php
@@ -0,0 +1,203 @@
+<?php
+/**
+ * Blocks API: WP_Block_List class
+ *
+ * @package WordPress
+ * @since 5.5.0
+ */
+
+/**
+ * Class representing a list of block instances.
+ *
+ * @since 5.5.0
+ */
+class WP_Block_List implements Iterator, ArrayAccess, Countable {
+
+	/**
+	 * Original array of parsed block data, or block instances.
+	 *
+	 * @since 5.5.0
+	 * @var array[]|WP_Block[]
+	 * @access protected
+	 */
+	protected $blocks;
+
+	/**
+	 * All available context of the current hierarchy.
+	 *
+	 * @since 5.5.0
+	 * @var array
+	 * @access protected
+	 */
+	protected $available_context;
+
+	/**
+	 * Block type registry to use in constructing block instances.
+	 *
+	 * @since 5.5.0
+	 * @var WP_Block_Type_Registry
+	 * @access protected
+	 */
+	protected $registry;
+
+	/**
+	 * Constructor.
+	 *
+	 * Populates object properties from the provided block instance argument.
+	 *
+	 * @since 5.5.0
+	 *
+	 * @param array[]|WP_Block[]     $blocks            Array of parsed block data, or block instances.
+	 * @param array                  $available_context Optional array of ancestry context values.
+	 * @param WP_Block_Type_Registry $registry          Optional block type registry.
+	 */
+	public function __construct( $blocks, $available_context = array(), $registry = null ) {
+		if ( ! $registry instanceof WP_Block_Type_Registry ) {
+			$registry = WP_Block_Type_Registry::get_instance();
+		}
+
+		$this->blocks            = $blocks;
+		$this->available_context = $available_context;
+		$this->registry          = $registry;
+	}
+
+	/**
+	 * Returns true if a block exists by the specified block index, or false
+	 * otherwise.
+	 *
+	 * @since 5.5.0
+	 *
+	 * @link https://www.php.net/manual/en/arrayaccess.offsetexists.php
+	 *
+	 * @param string $index Index of block to check.
+	 * @return bool Whether block exists.
+	 */
+	public function offsetExists( $index ) {
+		return isset( $this->blocks[ $index ] );
+	}
+
+	/**
+	 * Returns the value by the specified block index.
+	 *
+	 * @since 5.5.0
+	 *
+	 * @link https://www.php.net/manual/en/arrayaccess.offsetget.php
+	 *
+	 * @param string $index Index of block value to retrieve.
+	 * @return mixed|null Block value if exists, or null.
+	 */
+	public function offsetGet( $index ) {
+		$block = $this->blocks[ $index ];
+
+		if ( isset( $block ) && is_array( $block ) ) {
+			$block                  = new WP_Block( $block, $this->available_context, $this->registry );
+			$this->blocks[ $index ] = $block;
+		}
+
+		return $block;
+	}
+
+	/**
+	 * Assign a block value by the specified block index.
+	 *
+	 * @since 5.5.0
+	 *
+	 * @link https://www.php.net/manual/en/arrayaccess.offsetset.php
+	 *
+	 * @param string $index Index of block value to set.
+	 * @param mixed  $value Block value.
+	 */
+	public function offsetSet( $index, $value ) {
+		if ( is_null( $index ) ) {
+			$this->blocks[] = $value;
+		} else {
+			$this->blocks[ $index ] = $value;
+		}
+	}
+
+	/**
+	 * Unset a block.
+	 *
+	 * @since 5.5.0
+	 *
+	 * @link https://www.php.net/manual/en/arrayaccess.offsetunset.php
+	 *
+	 * @param string $index Index of block value to unset.
+	 */
+	public function offsetUnset( $index ) {
+		unset( $this->blocks[ $index ] );
+	}
+
+	/**
+	 * Rewinds back to the first element of the Iterator.
+	 *
+	 * @since 5.5.0
+	 *
+	 * @link https://www.php.net/manual/en/iterator.rewind.php
+	 */
+	public function rewind() {
+		reset( $this->blocks );
+	}
+
+	/**
+	 * Returns the current element of the block list.
+	 *
+	 * @since 5.5.0
+	 *
+	 * @link https://www.php.net/manual/en/iterator.current.php
+	 *
+	 * @return mixed Current element.
+	 */
+	public function current() {
+		return $this->offsetGet( $this->key() );
+	}
+
+	/**
+	 * Returns the key of the current element of the block list.
+	 *
+	 * @since 5.5.0
+	 *
+	 * @link https://www.php.net/manual/en/iterator.key.php
+	 *
+	 * @return mixed Key of the current element.
+	 */
+	public function key() {
+		return key( $this->blocks );
+	}
+
+	/**
+	 * Moves the current position of the block list to the next element.
+	 *
+	 * @since 5.5.0
+	 *
+	 * @link https://www.php.net/manual/en/iterator.next.php
+	 */
+	public function next() {
+		next( $this->blocks );
+	}
+
+	/**
+	 * Checks if current position is valid.
+	 *
+	 * @since 5.5.0
+	 *
+	 * @link https://www.php.net/manual/en/iterator.valid.php
+	 */
+	public function valid() {
+		return null !== key( $this->blocks );
+	}
+
+	/**
+	 * Returns the count of blocks in the list.
+	 *
+	 * @since 5.5.0
+	 *
+	 * @link https://www.php.net/manual/en/countable.count.php
+	 *
+	 * @return int Block count.
+	 */
+	public function count() {
+		return count( $this->blocks );
+	}
+
+}
diff --git a/wp-includes/class-wp-block.php b/wp-includes/class-wp-block.php
new file mode 100644
index 0000000000..979fca9070
--- /dev/null
+++ b/wp-includes/class-wp-block.php
@@ -0,0 +1,233 @@
+<?php
+/**
+ * Blocks API: WP_Block class
+ *
+ * @package WordPress
+ * @since 5.5.0
+ */
+
+/**
+ * Class representing a parsed instance of a block.
+ *
+ * @since 5.5.0
+ * @property array $attributes
+ */
+class WP_Block {
+
+	/**
+	 * Original parsed array representation of block.
+	 *
+	 * @since 5.5.0
+	 * @var array
+	 */
+	public $parsed_block;
+
+	/**
+	 * Name of block.
+	 *
+	 * @example "core/paragraph"
+	 *
+	 * @since 5.5.0
+	 * @var string
+	 */
+	public $name;
+
+	/**
+	 * Block type associated with the instance.
+	 *
+	 * @since 5.5.0
+	 * @var WP_Block_Type
+	 */
+	public $block_type;
+
+	/**
+	 * Block context values.
+	 *
+	 * @since 5.5.0
+	 * @var array
+	 */
+	public $context = array();
+
+	/**
+	 * All available context of the current hierarchy.
+	 *
+	 * @since 5.5.0
+	 * @var array
+	 * @access protected
+	 */
+	protected $available_context;
+
+	/**
+	 * List of inner blocks (of this same class)
+	 *
+	 * @since 5.5.0
+	 * @var WP_Block[]
+	 */
+	public $inner_blocks = array();
+
+	/**
+	 * Resultant HTML from inside block comment delimiters after removing inner
+	 * blocks.
+	 *
+	 * @example "...Just <!-- wp:test /--> testing..." -> "Just testing..."
+	 *
+	 * @since 5.5.0
+	 * @var string
+	 */
+	public $inner_html = '';
+
+	/**
+	 * List of string fragments and null markers where inner blocks were found
+	 *
+	 * @example array(
+	 *   'inner_html'    => 'BeforeInnerAfter',
+	 *   'inner_blocks'  => array( block, block ),
+	 *   'inner_content' => array( 'Before', null, 'Inner', null, 'After' ),
+	 * )
+	 *
+	 * @since 5.5.0
+	 * @var array
+	 */
+	public $inner_content = array();
+
+	/**
+	 * Constructor.
+	 *
+	 * Populates object properties from the provided block instance argument.
+	 *
+	 * The given array of context values will not necessarily be available on
+	 * the instance itself, but is treated as the full set of values provided by
+	 * the block's ancestry. This is assigned to the private `available_context`
+	 * property. Only values which are configured to consumed by the block via
+	 * its registered type will be assigned to the block's `context` property.
+	 *
+	 * @since 5.5.0
+	 *
+	 * @param array                  $block             Array of parsed block properties.
+	 * @param array                  $available_context Optional array of ancestry context values.
+	 * @param WP_Block_Type_Registry $registry          Optional block type registry.
+	 */
+	public function __construct( $block, $available_context = array(), $registry = null ) {
+		$this->parsed_block = $block;
+		$this->name         = $block['blockName'];
+
+		if ( is_null( $registry ) ) {
+			$registry = WP_Block_Type_Registry::get_instance();
+		}
+
+		$this->block_type = $registry->get_registered( $this->name );
+
+		$this->available_context = $available_context;
+
+		if ( ! empty( $this->block_type->uses_context ) ) {
+			foreach ( $this->block_type->uses_context as $context_name ) {
+				if ( array_key_exists( $context_name, $this->available_context ) ) {
+					$this->context[ $context_name ] = $this->available_context[ $context_name ];
+				}
+			}
+		}
+
+		if ( ! empty( $block['innerBlocks'] ) ) {
+			$child_context = $this->available_context;
+
+			if ( ! empty( $this->block_type->provides_context ) ) {
+				foreach ( $this->block_type->provides_context as $context_name => $attribute_name ) {
+					if ( array_key_exists( $attribute_name, $this->attributes ) ) {
+						$child_context[ $context_name ] = $this->attributes[ $attribute_name ];
+					}
+				}
+			}
+
+			$this->inner_blocks = new WP_Block_List( $block['innerBlocks'], $child_context, $registry );
+		}
+
+		if ( ! empty( $block['innerHTML'] ) ) {
+			$this->inner_html = $block['innerHTML'];
+		}
+
+		if ( ! empty( $block['innerContent'] ) ) {
+			$this->inner_content = $block['innerContent'];
+		}
+	}
+
+	/**
+	 * Returns a value from an inaccessible property.
+	 *
+	 * This is used to lazily initialize the `attributes` property of a block,
+	 * such that it is only prepared with default attributes at the time that
+	 * the property is accessed. For all other inaccessible properties, a `null`
+	 * value is returned.
+	 *
+	 * @since 5.5.0
+	 *
+	 * @param string $name Property name.
+	 * @return array|null Prepared attributes, or null.
+	 */
+	public function __get( $name ) {
+		if ( 'attributes' === $name ) {
+			$this->attributes = isset( $this->parsed_block['attrs'] ) ?
+				$this->parsed_block['attrs'] :
+				array();
+
+			if ( ! is_null( $this->block_type ) ) {
+				$this->attributes = $this->block_type->prepare_attributes_for_render( $this->attributes );
+			}
+
+			return $this->attributes;
+		}
+
+		return null;
+	}
+
+	/**
+	 * Generates the render output for the block.
+	 *
+	 * @since 5.5.0
+	 *
+	 * @param array $options {
+	 *   Optional options object.
+	 *
+	 *   @type bool $dynamic Defaults to 'true'. Optionally set to false to avoid using the block's render_callback.
+	 * }
+	 * @return string Rendered block output.
+	 */
+	public function render( $options = array() ) {
+		global $post;
+		$options = wp_parse_args(
+			$options,
+			array(
+				'dynamic' => true,
+			)
+		);
+
+		$is_dynamic    = $options['dynamic'] && $this->name && null !== $this->block_type && $this->block_type->is_dynamic();
+		$block_content = '';
+
+		if ( ! $options['dynamic'] || empty( $this->block_type->skip_inner_blocks ) ) {
+			$index = 0;
+			foreach ( $this->inner_content as $chunk ) {
+				$block_content .= is_string( $chunk ) ?
+					$chunk :
+					$this->inner_blocks[ $index++ ]->render();
+			}
+		}
+
+		if ( $is_dynamic ) {
+			$global_post   = $post;
+			$block_content = (string) call_user_func( $this->block_type->render_callback, $this->attributes, $block_content, $this );
+			$post          = $global_post;
+		}
+
+		if ( ! empty( $this->block_type->script ) ) {
+			wp_enqueue_script( $this->block_type->script );
+		}
+
+		if ( ! empty( $this->block_type->style ) ) {
+			wp_enqueue_style( $this->block_type->style );
+		}
+
+		/** This filter is documented in src/wp-includes/blocks.php */
+		return apply_filters( 'render_block', $block_content, $this->parsed_block );
+	}
+
+}
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 875fc763b7..2f12fec3c4 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.5-alpha-48158';
+$wp_version = '5.5-alpha-48159';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.
diff --git a/wp-settings.php b/wp-settings.php
index f351d84cfb..6fbef53916 100644
--- a/wp-settings.php
+++ b/wp-settings.php
@@ -278,6 +278,8 @@ require ABSPATH . WPINC . '/class-wp-block-pattern-categories-registry.php';
 require ABSPATH . WPINC . '/class-wp-block-patterns-registry.php';
 require ABSPATH . WPINC . '/class-wp-block-styles-registry.php';
 require ABSPATH . WPINC . '/class-wp-block-type-registry.php';
+require ABSPATH . WPINC . '/class-wp-block.php';
+require ABSPATH . WPINC . '/class-wp-block-list.php';
 require ABSPATH . WPINC . '/class-wp-block-parser.php';
 require ABSPATH . WPINC . '/blocks.php';
 require ABSPATH . WPINC . '/blocks/archives.php';