The pygmy marmoset (Cebuella pygmaea) is the smallest monkey in the world and one of the smallest primates overall. Native to the rainforests of the Amazon Basin in South America, it is known for its diminutive size, agility, and unique behaviour.

Pygmy marmosets are incredibly tiny, with a body length (excluding the tail) of only 12-15 cm (4.7-6 inches). Their tails are longer than their bodies, measuring about 17-23 cm (6.7-9 inches).

They typically weigh between 100 and 140 grams (3.5 and 5 ounces), making them the smallest species of monkey in the world.

These monkeys have brownish-gold fur with hints of grey, orange, and white. Their dense coat provides insulation in their forest environment. Their long tail is non-prehensile, meaning it doesn't grip objects like some other monkeys' tails, but it helps with balance as they move through the trees.

Pygmy marmosets have sharp claws (instead of flat nails like most primates) that help them grip tree trunks and branches.

Pygmy marmosets are gummivores, which means they primarily feed on tree sap or gum. They use their sharp lower incisors to gnaw small holes in tree bark, stimulating sap flow.

Pygmy marmosets are highly social and live in family groups of 2 to 9 individuals. These groups are typically composed of a dominant breeding pair and their offspring.

Social grooming and vocalisations are important for maintaining group bonds. They communicate using high-pitched calls, some too high for humans to hear. Territorial disputes are resolved through vocal displays rather than physical confrontations.