Div 100％高度显示为0px？

I'm currently building a website and have a small problem that i cant seem to tackle, I have created a div with a height of 100%, inside that div is a slider div also with a height of 100%, the problem is the first div displays a height of 0px so that the div that should come below the slider div displays behind the slider div, anyone that can help me?I'm currently building a website and have a sma