The Particle Zoo is a collection of more than 36 plush versions of subatomic particles from the worlds of physics and astronomy. Often compared to Giant Microbes, these handmade soft toys represent the familiar neutron and proton as well as lesser-known particles like the charm quark and muon. A favorite of physics students can make unique birthday and graduation gifts, especially for physics students. The particles are handmade in the USA. "There are no other companies making plush subatomic particles, so they are a unique concept. Because they are weighted according to their relative masses, they can serve as a teaching aid or novelty gift," Julie Peasley, owner and seamstress for The Particle Zoo, told TDmonthly. Launch date: 2008.