The bryophyte herbarium at the W. Szafer Institute of Botany PAS (KRAM B) is the largest collection of these plants in Poland and one of the largest in Central Europe. At the end of October 2021, it consisted of 261,000 accessioned specimens of mosses, liverworts and hornworts and this number apparently locates it among the top 40 largest bryophyte herbaria of the world. In addition, there are about 60,000 specimens in the herbarium, which are still awaiting to be processed and accessioned into the main collection. The herbarium holds also over 2,000 type specimens, i.e. specimens that were used to describe new taxa of bryophytes. These are the most valuable items which determine the unique status of each herbarium compared to other similar collections. In total, the KRAM B contains about 80% of all known species of moss, representing approximately 90% of all traditionally conceived genera of these plants in the world. Particularly noteworthy is the world’s largest collection of mosses and liverworts from the austral polar regions, including unique collections from the Antarctic and all the islands of the Southern Ocean, especially Îles Crozet, Îles Kerguelen and the Prince Edward Islands, South Georgia and Heard Island. In addition, there are significant collections of mosses from tropical Africa and southern South America, Australia, Tasmania, New Zealand and China. The herbarium includes almost all historical collections of bryophytes from the area of Poland from the beginning of the 19th century, including the oldest by H. Łobarzewski and A. Rehmann, and all the most important later Polish collections from the 19th and 20th centuries, including those of J. Krupa, I Szyszyłowicz, T. Chałubiński, M. Raciborski and A. Żmuda. The herbarium of bryophytes at KRAM keeps also numerous series of exsiccatae, which are incorporated into the main collection, although they are usually preserved in separate folders. Some historical exsiccatae deserve special attention because they contain many type specimens.