NON-TECHNICAL SUMMARY Light-responsive molecules have emerged as a new tool to optically control various properties of solid-state materials. Reversible control over the optical, thermal, phase, and mechanical properties of solid-state materials enables applications that involve optical storage, energy storage, and mechanical response. The fundamental understanding of the optically-induced molecular transformation in solids and how such transformation results in phase change, however, is currently lacking. This CAREER research project, jointly supported by the Solid State and Materials Chemistry program in the Division of Materials Research and the Chemical Structure, Dynamics, and Mechanisms B program in the Division of Chemistry, broadens the knowledge on light-molecule interactions in a condensed environment, which is translated to understand solar thermal energy storage that has a tremendous impact on the energy security of the nation. The project contributes to the advancement of various fields studying molecular switching, phase transition behaviors, and renewable solar energy storage. Additionally, it addresses critical areas for improving underrepresented minority engagement in STEM at Brandeis University and in the local community. Undergraduate students from underrepresented groups are actively recruited and trained in organic materials chemistry, and Spanish-English bilingual science events are established in partnership with a local high school to promote the int