Why is overflow interacting with z-index?

Question

I am trying to understand the rules behind z-index and how it interacts with the overflow property.

I have this html:

Answer 1

Absolute-positioned elements do not contribute to the dimensions of their parents.

Therefore, the .cell DIV has no content that affects its dimensions, making it 100% wide by 0px high.

To make the element appear, you'll have to add a height to .cell that will encompass the DIV, in this case 120px (70px top + 50px height).