The pygmy marmoset is the smallest primate in the world. Its maximum length is only about 30 cm, half of which is tail.

They feed on plant and tree saps which they find by biting a hole in the bark. The have elongated lower incisors for scraping out sap. They have claws, which is an adaptive feature that enables them to get a tighter grip on branches.

Like all other marmosets, they live in family troops with only one breeding pair. The offspring grow up with the parents and assist in caring for siblings. When a troop reaches a certain size, depending on the amount of food in the habitat area, some marmosets will leave the group, find mates and set up their own troop of families.