Dropdown menu in Yii2

Any link or tutorial for dropdown menu?

for example this is the default menu in advanced template




$menuItems = [

                ['label' => 'Home', 'url' => ['/site/index']],

                ['label' => 'About', 'url' => ['/site/about']],

                ['label' => 'Contact', 'url' => ['/site/contact']],

                

                

            ];



I want to add a sub-menu below About menu say "About Company", how I can do that?

Thanks in advance.