A superparamagnetic fluid, otherwise known as a <a href="https://en.wikipedia.org/wiki/ferrofluid" class="extiw" title="en:ferrofluid">ferrofluid</a>, in a dish over a <a href="https://en.wikipedia.org/wiki/neodymium" class="extiw" title="en:neodymium">neodymium</a> magnet.
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/jurvetson/">Steve Jurvetson</a>
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