Michael Rosen wants to understand how cells stay organized. His work focuses on enigmatic compartments within a cell, called biomolecular condensates, which concentrate proteins and nucleic acids without a surrounding membrane. These structures are involved in diverse cellular processes from RNA metabolism to signal transduction. Biomolecular condensates appear to form through the physical process of liquid-liquid phase separation. Rosen and his team use a range of tools and techniques, including in vitro and cellular microscopy and biochemical reconstitution, to investigate phase separation in engineered and natural condensates. Within this phase separation framework, the team is seeking a clearer understanding of how a cell regulates the assembly, composition, and function of these important structures.