The Small Business Innovation Research (SBIR) Program is an important National Institutes of Health (NIH) funding mechanism used to develop innovative solutions that address public health challenges. A major objective of the SBIR Program is to facilitate the commercialization of technologies developed by small business concerns (SBCs). Yet, the development of biomedical products is often impeded by a significant funding gap between the end of the SBIR Phase II award and the commercialization stage. This gap is increased by the barriers associated with technologies under development for small commercial markets, such as those focused on rare diseases or young pediatric populations. This Funding Opportunity Announcement (FOA) invites small businesses to submit SBIR grant applications to support later stage research and development (referred to as Phase IIB) for promising projects that were previously funded by SBIR or STTR (Small Business Technology Transfer) Phase II awards that address rare diseases or young pediatric populations (aged 0-12 years and defined in Section IV, part 7), and will require eventual Federal regulatory approval/clearance. The goal of this FOA and the resulting Phase IIB awards is to assist applicants in pursuing the next appropriate milestone(s) necessary to advance a product to regulatory approval and commercialization by promoting partnerships between small business awardees and third-party investors and/or strategic partners, including patient advocacy organizations.