You can choose to adorn your desk with an almost infinite number of trinkets, but we beg of you to ignore the Newton’s Cradles, or the Lavalamps, or even the decorative Rolodexes of old, and consider the Colourful Ferrofluid In a Bottle instead. Ferrofluid is a thick liquid that is mixed in with nano-scale iron particles. It doesn’t mix with water and tends to clump together. But in the presence of a magnet, the liquid comes to life. You can delight yourself and your guests, for at least 30 whole seconds, with the shapes the liquid will take inside the bottle. You can even “double your fun” by using two magnets. It’s a fun tabletop toy that costs $60.