Pygmy marmosets are from South America. At 3.5 ounces, they are the world's smallest monkey (but not quite the world's smallest primate — that honor goes to 2 ounce pygmy tarsier of central Sulawesi, Indonesia). Enjoy this video of pygmy marmosets enjoying some grapes, which look like beach balls in their hands.
Image: Aardvark video screengrab