The lichenological herbarium (Herb. Nimis, TSB) consists of approx. 42,000 samples, of which approx. 32,000 from Italy, collected especially by Pier Luigi Nimis and Mauro Tretiach. Approximately 4,000 infrageneric taxa are represented, of which 164 are holotypes and isotypes (including neotypes, paratypes, syntipes and topotypes). The herbarium has been established since 1979 and is completely computerized and can be consulted in a digital archive.

Before this date the only lichenological herbarium existing at the University of Trieste was that of Carlo Zirnich (1895 - 1978) consisting of a hundred samples, collected mainly on the Trieste and Slovenian Karst, and kept in a separate package.

The samples come from both Italy and Europe and from non-European countries, in particular Asia (mainly from Japan), Alaska-Yukon, Northern Ontario, Svalbard archipelago, Canary Islands, Southwestern United States (Arizona, California, New Mexico) ), Mexico and Tierra del Fuego.

The herbarium also includes samples of the Lichenes Selecti Exsiccati and the Lichenes Rariores Exsiccati distributed by A. Vežda, samples of the Plantae Graecenses published by the Institute of Systematic Botany of the University of Graz (Austria), as well as numerous samples obtained in exchange from L. Ferraro (Corrientes, Argentina), A. Ciccarelli (Mendoza, Argentina), O. Vitikainen (Helsinki, Finland), F. Rosentreter (Manitoba, Canada) and J. Poelt (Graz, Austria).

In 1989 a remarkable collection of lichens (840 samples), collected by Paolo Modenesi at the Italian base in Antarctica and preserved separately (ELA - TSB; resp.  Lucia Muggia), was received. The studies carried out in the framework of the National Program of Research in Antarctica have led to a profound revision of knowledge on the lichen flora of that Continent. A database on Antartic lichens has also been developed.

In September 2016 a voluminous annotated catalog of Italian lichens was published by Pier Luigi Nimis by the University Publishing House EUT (Nimis, 2016). All information on regional distribution, nomenclature, ecology, taxonomic notes were digitized and organized in an information system on Italian lichens freely available in ITALIC 5.0, created within the Dryades project of the Department of Life Sciences of the Trieste University. The database is also accompanied by an image gallery of more than 3,300 species.