diff --git a/src/Kunoichi/ThemeCustomizer/CustomizerSetting.php b/src/Kunoichi/ThemeCustomizer/CustomizerSetting.php
index f4e672b..d29ff4a 100644
--- a/src/Kunoichi/ThemeCustomizer/CustomizerSetting.php
+++ b/src/Kunoichi/ThemeCustomizer/CustomizerSetting.php
@@ -11,6 +11,8 @@ abstract class CustomizerSetting extends Singleton {
 	
 	use Utilities;
 	
+	protected $panel_id = '';
+	
 	protected $section_id = '';
 	
 	/**
@@ -44,9 +46,17 @@ protected function after_init() {
 	 * @param \WP_Customize_Manager $wp_customizer
 	 */
 	public function customize_register( $wp_customizer ) {
+		// Register panel.
+		$panel_setting = $this->panel_settings();
+		if ( $panel_setting ) {
+			$wp_customizer->add_panel( $this->panel_id, $panel_setting );
+		}
 		// Register setting if required.
 		$section_setting = $this->section_setting();
 		if ( $section_setting ) {
+			if ( $this->panel_id ) {
+				$section_setting[ 'panel' ] = $this->panel_id;
+			}
 			$wp_customizer->add_section( $this->get_section(), $section_setting );
 		}
 		// Register all fields.
@@ -76,6 +86,16 @@ protected function register_field( &$wp_customizer, $id, $args ) {
 		$wp_customizer->add_control( new $control_class( $wp_customizer, $id, $args ) );
 	}
 	
+	/**
+	 * If proper array returned, register panel.
+	 *
+	 * @see \WP_Customize_Manager::add_panel
+	 * @return array
+	 */
+	protected function panel_settings() {
+		return [];
+	}
+	
 	/**
 	 * If array returned, register section.
 	 *
diff --git a/tests/src/Kunoichi/ThemeCustomizerTest/NestedCustomizer.php b/tests/src/Kunoichi/ThemeCustomizerTest/NestedCustomizer.php
new file mode 100644
index 0000000..91172d1
--- /dev/null
+++ b/tests/src/Kunoichi/ThemeCustomizerTest/NestedCustomizer.php
@@ -0,0 +1,40 @@
+<?php
+
+namespace Kunoichi\ThemeCustomizerTest;
+
+
+use Kunoichi\ThemeCustomizer\CustomizerSetting;
+
+class NestedCustomizer extends CustomizerSetting {
+	
+	protected $panel_id = 'nested';
+	
+	protected $section_id = 'nested_child';
+	
+	protected function section_setting() {
+		return [
+			'title' => 'Nested Section',
+		];
+	}
+	
+	protected function panel_settings() {
+		return [
+			'title'       => 'Nested Panel',
+			'description' => 'This panel is added by Kunoichi Theme Customizer.',
+			'priority'    => 200,
+		];
+	}
+	
+	protected function get_fields() {
+		return [
+			'nested_section_1' => [
+				'label' => 'Nested Field 1',
+			],
+			'nested_section_2' => [
+				'label' => 'Nested Field 2',
+			],
+		];
+	}
+	
+	
+}
diff --git a/tests/src/Kunoichi/ThemeCustomizerTest/SimpleCustomizer.php b/tests/src/Kunoichi/ThemeCustomizerTest/SimpleCustomizer.php
index 5809bb0..b78d554 100644
--- a/tests/src/Kunoichi/ThemeCustomizerTest/SimpleCustomizer.php
+++ b/tests/src/Kunoichi/ThemeCustomizerTest/SimpleCustomizer.php
@@ -12,7 +12,7 @@
  */
 class SimpleCustomizer extends CustomizerSetting {
 	
-	protected $section_id = 'site-setting';
+	protected $section_id = 'title_tagline';
 	
 	
 	/**
@@ -21,8 +21,8 @@ class SimpleCustomizer extends CustomizerSetting {
 	protected function get_fields() {
 		return [
 			'site_setting_title' => [
-				'label'       => __( 'Title' ),
-				'description' => '',
+				'label'       => 'Added Title',
+				'description' => 'This section is added by Kunoichi Theme Customizer.',
 			],
 		];
 	}
diff --git a/tests/test-utility.php b/tests/test-utility.php
index 360d67d..a3ad1bb 100644
--- a/tests/test-utility.php
+++ b/tests/test-utility.php
@@ -21,5 +21,4 @@ public function test_translation() {
 		switch_to_locale( 'ja' );
 		$this->assertEquals( 'メタ情報とSEO', __( 'Meta and SEO', 'theme-customizer' ) );
 	}
-
 }
diff --git a/theme-customizer.php b/theme-customizer.php
index 5ca9e7b..c081544 100644
--- a/theme-customizer.php
+++ b/theme-customizer.php
@@ -16,14 +16,16 @@
 if ( ! defined( 'ABSPATH' ) ) {
 	die( 'Invalid request.' );
 }
-
 require __DIR__ . '/vendor/autoload.php';
 
 \Kunoichi\ThemeCustomizer::load_locale( get_locale() );
 
-$auto_loaded = [ 'Patterns' ];
-foreach ( $auto_loaded as $dir ) {
-	$path = __DIR__ . '/src/Kunoichi/ThemeCustomizer/' . $dir;
+$auto_loaded = [
+	[ __DIR__ . '/src', 'Kunoichi/ThemeCustomizer/Patterns' ],
+	[ __DIR__ . '/tests/src/', 'Kunoichi/ThemeCustomizerTest' ],
+];
+foreach ( $auto_loaded as list( $base, $dir ) ) {
+	$path = $base . '/' . $dir;
 	if ( ! is_dir( $path ) ) {
 		continue;
 	}
@@ -32,7 +34,7 @@
 			continue;
 		}
 		list( $file, $class_name ) = $match;
-		$class_name = "Kunoichi\\ThemeCustomizer\\{$dir}\\{$class_name}";
+		$class_name = str_replace( '/', "\\", $dir ) . "\\" . $class_name;
 		if ( ! class_exists( $class_name ) ) {
 			continue;
 		}