Pigmy Marmoset

The pigmy marmoset is one of the world's smallest primates, sitting here on a young boy's fingers. A full grown pigmy marmoset weighs only 3 ounces (86 g) and measures a short six inches (15 cm). It eats berries, buds, fruits, and arthropods (insects and spiders, that is). It also gets a lot of nourishment from sucking the juices from trees.

Marmosets are monkeys of the family Callitrichidae. While they are among the cutest animals in the world, I don't think they live very long as pets.