The National Science Foundation's Systems Science (SYS) program supports fundamental research aimed at developing a theoretical foundation for design and systems engineering. The program seeks intellectual advances that integrate underlying theories, such as probability theory, decision theory, and organizational sociology, to create general, domain-independent explanatory models for design and systems engineering. Successful proposals should address research topics like search strategies, organizational structures, and the creation and assessment of design models. The program is open to a wide range of applicant types, and research that focuses on domain-specific applications but also advances the fundamental understanding of design and systems engineering may be considered for co-funding with other programs. Typical awards under this program range from $250,000 to $650,000, with project periods spanning 3-5 years. The funding is provided through grants, and the awards are expected to support projects that advance scientific understanding, develop new technologies, and address national priorities in fields such as artificial intelligence, advanced manufacturing, and quantum information science.