The fluffy caterpillars of the family Megalopygidae!
This particular caterpillar was found at Posada Amazonas lodge in Tambopata, Peru, and it is almost a fully grown caterpillar belonging to the family Megalopygidae, also collectively known as Flannel Moths. This family of moths is known for having hairy caterpillars, which look all fluffy, cute and cuddly (doesn't this pic look a bit like Donald Trump's wig? :-D).
And although it may look inviting to you, hidden beneath the soft hairs are poisonous spines. If they are handled the spines may break, releasing a chemical which causes excruciating pain, and will also pierce the skin. It can also cause an extreme allergic reaction resulting in rashes, blisters, inflammation, and breathing difficulty. So, if you're in Peru or anywhere in North America or the New World Tropics where these are usually found, and you come across these, do remember the hidden spines and don't pick it up!
The adults, by comparison, are somewhat dull being blackish or ochreous in colour. (images in Source 1).