This IRG establishes the materials science of biomolecular condensates, the membraneless assemblies that cells form by liquid-liquid phase separation. It relates biomolecular sequence and composition to condensate material properties such as interfacial tension, viscoelasticity, and molecular partitioning, and encodes those properties on demand. The team integrates chemically specific coarse-grained simulation, machine-learning models of the sequence-to-property relationship, continuum theories of multiphase morphology and coarsening, and quantitative experiments that use microfluidics, micropipette aspiration, and multi-wavelength optogenetic control to characterize and reconfigure condensates, with target demonstrations as actuators, microreactors, and capture-and-release vessels.