The Limnology and Algology collections comprise more than 9,000 specimens. Of these, more than two thirds consist of microscopic organisms such as diatom algae, cyanobacteria, zoobenthos, and zooplankton collected mainly in the Alps and in Trentino during the numerous research projects conducted by the MUSE since the nineties. In addition to these relatively recent collections, there are also four historical collections of algae with exsiccates of marine and freshwater algae collected mainly in the nineteenth century from different places around the world.