The Golden Lion Tamarin (Leontopithecus rosalia) is a very small monkey of the Mata Atlanitca, the coastal rainforest of Brazil, but it is a shining star for species conservation efforts. By the late 1970s both, their habitat and their population numbers were nearly dashed with only 150 animals left in the isolated remains of the forest. Through a very successful reintroduction project conducted by the members of the Associação Mico-Leão-Dourado in the Poço das Antas Reserve there are today more than 1000 free-ranging Golden Lion Tamarins living north of Rio de Janeiro. In each group one adult female is equipped with a radio transmitter to enable the researchers to keep track of them and capture the whole family to mark the new offspring and study the development of the individuals. The actual goal of the Associação Mico-Leão-Dourado is to pass the 2000 individuals mark by the year 2025. Meanwhile the Golden Lion Tamarin has become an ambassador for the whole Mata Atlantica. This shrinking forest is so rich in species that it urgently needs and deserves to step out of the shadow of the Amazonian rainforest which receives much more attention.