2. Pygmy Marmoset
This cute little monkey is commonly found in the rainforests of the western Amazon basin in South America. The Pygmy Marmoset is deemed as the smallest primate and the smallest monkey, weighing just over 100 grams, and measuring 117 – 152 mm from its head to its body and 172-229 mm on its tail. They usually inhabit the evergreen as well as forests by the river and is known for being a gumivore.