Discovering the world’s biota underpins the study of the origins, evolution, and maintenance of biodiversity. Yet despite centuries of exploration, our knowledge of the diversity of life is still temporally and spatially biased, and critical areas of extant and extinct biodiversity remain undiscovered or undocumented. This restricts our ability to develop a comprehensive and comparative evolutionary framework for all life and hinders our understanding of the mechanisms and processes of evolution. To address this issue, the Division of Environmental Biology (DEB) in the Directorate of Biological Sciences (BIO) encourages the submission of proposals to the Systematics and Biodiversity Sciences (SBS) cluster to support research on Poorly Sampled and Unknown Taxa (PurSUiT). The PurSUiT category is meant to encourage biodiversity discovery and description in poorly known, or dark areas, of the Tree of Life. Its incorporation as a special category within SBS reflects a continued effort to close significant gaps in biodiversity knowledge. Proposals submitted to this category should address expeditionary and exploratory research on organismal diversity that occurs, or used to occur, in natural environments and should aim to advance the discovery, identification, description, classification, and cataloguing of the world’s unknown extant and extinct biodiversity. Research projects must address compelling biodiversity discovery questions and must entail a primarily clade- or guild-based approach (e.g., regional, global, or planetary inventories). Priority will be given to innovative projects that fill significant gaps in biodiversity knowledge and integrate taxon information within an evolutionary or taxonomic framework.