Star and planet formation occur at the same time, in regions of the Galaxy less than about 10 million years old. Most stars in the Galaxy form in dense groups or clusters. This research will produce the most comprehensive and detailed study to date of the dust disks with the potential to form planets surrounding stars in these typical, dense star-forming regions. In previously-funded work, the investigator obtained the basic data for this new program and published the first results in scientific journals. Here, the investigators will combine these data with available supporting data from other scientists, increase the amount of data with the results from new telescopic observations, and analyze all of the data. These results will constrain theoretical models of planet, dust disk, and clustered star formation. This project supports the mission of the NSF by promoting our understanding of the formation of planet-forming disks in dense, clustered star forming regions. The lead investigator will include a student from a non-traditional background in the research project, and will share the research results with classes that he teaches and through public evening lectures. This research will produce the most comprehensive and highest angular resolution study to date of potentially planet-forming disks in clustered star forming regions. Such dense, transient, short-lived clusters contain from 100 to over 1000 forming stars inside self-gravitating, parsec diameter clumps within giant molecular clouds where outflow feedback, UV radiation, stellar winds, and supernovae shape the environment of planet formation. The expected results will include the circumstellar masses within the planet-forming zones of hundreds of coeval protoplanetary disks, the size distribution for these disks, constraints on other disk parameters such as scale height and surface density profile, and relationships between disk, stellar, and environmental properties. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.