Smallest monkey

Pygmy marmosets (Callithrix pygmaea) weight a mere 15 g (0.53 oz) at birth and grow to an average adult weight of just 119 g (4.20 oz). They measure, on average, 136 mm (5.35 in) excluding tail, which is usually longer than the body, and can be found in the upper Amazon, in the evergreen forests of Peru, Ecuador, Colombia, Bolivia, and Brazil. Despite their size, pygmy marmosets can leap up to 5 m (16 ft 5 in) into the air!