Centering 2 Divs inside another vertically

Question

I have 2 divs that I want to centre vertically inside another div. At the moment I have:

http://jsfiddle.net/5vpA3/1/

Now I understand what is going on here, but

Answer 1

Flexbox solution to center vertically:

#container {
    display: flex;
    align-items: center;
}

OP's original fiddle modified: http://jsfiddle.net/o3pmyb8c/

If you would like to also center horizontally you can add justify-content: center;