Bryophytes are small and structurally simple plants consisting of around 20, 000 species distributed in three evolutionary lineages (mosses, liverworts, and hornworts). Bryophytes usually occupy harsh environments where other photosynthetic organisms are little competitive. This capacity is based on the tolerance of bryophytes to adverse environmental factors (particularly desiccation) and their economy in production, which in turn are found on diverse physiological mechanisms and ecological adaptations. One of these mechanisms is the outstanding capacity of bryophytes to produce bioactive compounds with diverse biological functions. In particular, liverworts can synthesize a great variety of terpenoids, and the three bryophyte lineages can produce phenolic derivatives (from simple cinnamic acids to complex flavonoids), alkaloids, and lipids. These compounds, many of them specific, contribute to the development of special smells and flavors and may have both positive (antibiotic, fungicidal, deterrent, herbicidal, antioxidant, cytotoxic, antidiabetic) and negative (allergenic) properties for human beings. Bisbibenzyls and sesquiterpenoid derivatives in liverworts and the diterpenoid derivatives momilactones in mosses are the most relevant compounds. Of particular interest is the recent possibility to use model bryophytes (the moss Physcomitrella patens and the liverwort Marchantia polymorpha) as biotechnological tools (in bioreactors) to produce pharmaceutical substances. Overall, and despite the advances experienced in the past decades, biotechnological substances have only been studied in a relatively small number of bryophyte species, and thus, this discipline has a strong research potential for the future. © 2021 Elsevier Inc.