Liquid-liquid phase separation (LLPS) of biomacromolecules such as DNA, RNA, and proteins plays key roles in sophisticated biological processes in real cells, including transcription, compartmentalization of multiple enzymes, stress response, and enzymatic reactions. LLPS induces the formation of three-dimensional sphereshaped dense structures dispersed in dilute phase, which are called LLPS droplets or simply droplets. The peculiar physical states of LLPS droplets are responsible for processes such as reactant accumulation, compartmentalization of several enzymes, activation and deactivation of enzymatic activities, and maturation of proteins into gels or fibrils. Therefore, developing experimental models of biomacromolecule LLPS droplets to perform biophysical analysis in vitro have been desired.