Tropical rainforests are one of the most species-rich areas on earth. Thousands of animal and plant species live there. The smaller microbial protists, which are not visible to the naked eye, are also native to these forests, where they live in the soils and elsewhere. A team of researchers has examined them more closely by analyzing their DNA. They discovered many unknown species, including many parasites, which may contribute to the stability of rainforest ecosystems.