How do I create a pull down menu using Javascript?

I am creating a recipe web page and I am having trouble trying to figure out how to create the pull down menus. I want to have the categories such as appetizers, soups, desserts, main dishes, etc to show and then when i scroll over them with my mouse or click on each one, I get a pull down menu of types of food I could make in each category. Can someone help me please?