The Advancing Digitization of Biological Collections (ADBC) program seeks to enhance and expand the national resource of digital data documenting existing vouchered biological and paleontological collections and to advance scientific knowledge by improving access to digitized information (including images) residing in vouchered scientific collections across the United States. The information associated with various collections of organisms, such as geographic, paleogeographic and stratigraphic distribution, environmental habitat data, phenology, information about associated organisms, collector field notes, and tissues and molecular data extracted from the specimens, is a rich resource providing the baseline from which to further biodiversity research and provide critical information about existing gaps in our knowledge of life on earth. The national resource is structured at three levels: a central coordinating organization, a series of thematic networks based on an important research theme, and the physical collections. This solicitation focuses on proposals for Thematic Collections Networks (TCN) and proposals for Partners to Existing Networks (PEN) to link with existing TCNs, outlined below.  TCN proposals will be submissions for two- to four-year awards based on a particular research theme. This research theme may be a grand challenge for biodiversity, a part of a grand challenge, or another important research theme requiring information from existing collections. The collaborating institutions will conduct the actual digitization of the specimens (including imaging and mobilization of the data). PEN proposals to partner with and further the efforts of ongoing NSF-funded TCNs are encouraged. The new partners must increase the number of specimens digitized in the ongoing project and fill gaps not addressed by the specimens in the existing TCN.