The Division of Chemical, Bioengineering, Environmental, and Transport Systems (CBET) and the Division of Chemistry (CHE) are conducting a Re-entry to Active Research (RARE) program to reengage, retrain, and broaden participation within the academic workforce. The primary objective of the RARE program is to catalyze the advancement along the academic tenure-track of highly meritorious individuals who are returning from a hiatus from active research. By providing re-entry points to active academic research, the RARE program will reinvest in the nations most highly trained scientists and engineers, while broadening participation and increasing diversity of experience. A RARE research proposal must describe potentially transformative research that falls within the scope of participating CBET or CHEprograms. The RARE program includes two Tracks to catalyze the advancement of investigators along the academic tenure system after a research hiatus, either to a tenure-track position or to a higher-tenured academic rank. Track 1 of the RARE program reengages investigators in a competitive funding opportunity with accommodations for gap in record that are a result of the research hiatus. A Track 1 proposal will follow the budgetary guidelines of the relevant CBET program for an unsolicited research proposal or the relevant CHE Disciplinary Research program. Track 2 retrains investigators for whom the research hiatus has led to the need for new or updated techniques, such that retraining is required to return the investigator to competitive research activity. A description of how these new techniques will lead to competitive research in CBET or CHE programs is required. A Track 2 proposal budget will include only funds necessary for specific retraining activities, such as travel to a workshop or conference, workshop registration fees, a retraining sabbatical, or seed funding to support collection of preliminary data (including salary support, equipment usage fees, materials, and/or supplies). General inquiries regarding this program should be made to: RAREquestions@NSF.GOV or a RARE Program Officer listed below.