Drop-Down List within a Drop-Down List

Hello,

I essentially would like to create a drop-down menu within a drop-down menu. For example: I open a drop-down menu, hover my cursor over one of the options which then opens a second drop-down menu on the side, from which I can select an option.

I would equate this to a retail website where you can hover the cursor over "Men" or "Women", and it then shows a menu of the different types of clothing you can select from.

I do NOT want to have two columns of data.

Could anyone help?