How to animate swapping grid positions in css3?

Problem

I was looking at http://stackexchange.com/sites where clicking on an image swaps with another seemingly random image, and it looks like a really cool effect, and was trying to figure out how it was implemented - is it some sort of plugin? Also not sure if there is a proper name for this effect - if so, what it is?

Problem courtesy of: justclaire

Solution

They are using a jquery plugin called isotope: http://isotope.metafizzy.co/

Solution courtesy of: Matt Berkowitz

Discussion

for similar effects http://stackexchange.com/sites

you can find from here: http://packery.metafizzy.co/

Discussion courtesy of: Rakesh Singh

This recipe can be found in it's original form on Stack Over Flow.