Theme making, dont show child categories…

So iv been making a theme but im a little stuck with this, i want to make a navigation bar of categories and drop downs for the children categories but i can figure out how to do this, if any one could help then it would be great.

This is my current command but displays all, including child and no dropdowns. Almost like they are all parent.

<?php wp_list_categories('show_count=0&title_li=0&hide_empty=0'); ?>