Marmosets are New World Monkeys, which means that it comes from a family of primates that is found in Central and South America. Marmosets specifically are found for the most part in Brazil which is where they are native to. They are very small monkeys - males are on average 7.4 inches tall and weigh around 256g, and females are on average 7.3 inches tall and weigh around 236g. They are tree dwelling and move about in a very similar fashion to squirrels!
They mainly eat insects and plant exudates (saps, gums, latex and resins). They get to the exudates by clinging on to the tree with their claw like nails and chewing a hole in the tree. They can then lick them up! They also like fruit, insects, bird eggs, small chicks and mammals and some small reptiles and amphibians.
In the wild marmosets live in extended family groups of up to 15 with only a few breeding members such as one male and one or two females. The other members of the group will help to bring up the young. Gestation period is 5 months and they can give birth twice a year. Females usually give birth the non-identical twins, as Cuiaba has done. The father helps carry them around until they get brave enough to begin jumping around!
Here's a video of when Paolo came to the Zoo to join Cuiaba.