Presently, bryophytes (liverworts, mosses, hornworts) are second-most diverse clades of land plants occurring in a wide array of ecosystems. The bryophytes represent the earliest land plant lineages, of which origin and evolutionary processes remain equivocal. In general, our understanding for the interactions of bryophytes and arthropods has been arrested by the dearth of biological studies and bryophyte fossil records. Some insect clades have been intimately associated with liverworts and mosses, which include thallus-mining rhagionid flies and foliage-feeding micropterigid moths. The biology of extant bryophyte-feeders can provide clues for understanding the history of bryophyte-arthropod interactions. On the other hand, bryophyte fossils that harbor traces caused by herbivores manifest the biological interactions in geologic time; such evidence has been found on the earliest fossil liverwort from the Middle Devonian. An examination of a diverse anatomically preserved plant assemblage of the Early Cretaceous Vancouver Island has revealed some plant tissues with presumable arthropod herbivory, arthropod coprolites, and bacterial/fungal infections in some fossilized mosses and thallose liverworts, and has unexpectedly led to a discovery of mycorrhizal root nodules in a coeval conifer. My views on future research of biological interactions across time by examining both fossil and extant species will be introduced.