New World Monkeys:
* Marmosets: These are the smallest monkeys in the world, with some species reaching only 5 inches in length and weighing less than 5 ounces. They are characterized by their small size, silky fur, and long, non-prehensile tails.
* Tamarins: Tamarins are slightly larger than marmosets but still quite small. They can range from 6 to 15 inches in length and weigh between 10 and 30 ounces. They have longer legs than marmosets and their tails are usually bushy.
Old World Monkeys:
* De Brazza's Monkey: These monkeys, found in Central Africa, can be quite small, reaching a length of around 20 inches and weighing 10-15 pounds. They are known for their striking blue face and white beard.
Note: While these monkeys are considered "small," it's important to remember that size can vary depending on species and even individual variations within a species.
It's also worth noting that these monkeys, despite their small size, are still incredibly intelligent and complex creatures with fascinating social structures and behaviors.