lava lamps
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/17997843@N02">Dean Hochman</a> from Overland Park, Kansas, U.S.
CC BY 2.0
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/deanhochman/16136876840/">lava lamps</a>