Biomolecular condensates exhibit distinct material properties that are intimately linked to their functions. A major open question is how the properties of biomolecules shape emergent condensate behaviors. Experimental approaches have provided valuable insights into bulk material properties, yet direct observation of individual molecules within condensates remains challenging. Complementing experiments, molecular simulations have become indispensable in helping bridge scales from molecules to mesoscale assemblies. In this review, we discuss methodological advances in experiments and simulation that elucidate the relationships between molecular properties and condensate behavior and highlight frontiers in probing molecular ensembles within condensates. By integrating single-molecule perspectives with collective material properties, we outline emerging principles that connect microscopic interactions to macroscale condensate properties.