Loligo pealei (squid embryos), 5 days (80x),
Courtesy Nikon Small World Photo Micrography Competition: Photographed by Dr. Rachel Fink
These adorable little creatures look like a trio of dapper dandies stuffed into acorns, but they're actually mini-squids. The gestation period of squid eggs varies according to the temperature of the water in which they were laid (in warm climes, they can hatch in around 11 days; in colder waters, it can take up to 27). The embryos here are still young, but they're already differentiated enough to have eyestalks and mouths, and you can just make out the budding tentacles.