Ferrofluid is a pretty neat substance. Tiny, often magnetic microscopic particles are suspended in a liquid. Then, using regular magnets, or electromagnets, you can control what they do. It has many practical uses, but also the below artistic one (which also has a practical use as a clock).
You can buy the said clock, but it’s an “art piece” and comes with an “art piece” price of 7,500 euros, which at current exchange rates, is over $8,400. That’s alittle too much for me. Plus, the magnetic material only has a 1 month lifespan. I’m not sure why, but that means you would have to by replacements of that stuff for probably an equally high price.