A cell is the basic building block of life, controlling and localizing complex chemical reactions within subcellular compartments, each a distinct chemical environment. Compartmentalization, not just by organelles, thus defines the boundaries of biological systems by separating internal volume from external environment, which is essential for cellular activity. Compartments within cells are mostly labeled as cell organelles, many of which are separated by membranes, such as the mitochondria, which generates energy in the form of ATP, or lysosomes, which digest cellular waste/byproducts. However, membranes are not present in all organelles, such as stress granules, Cajal bodies, or nucleoli, which are assembled via liquidliquid phase separation (LLPS). Despite major recent advances in understanding biological phase separation, how cells and organelles, especially membraneless organelles, emerged and evolved is still unknown. One way to tackle this question is to investigate the mechanism of assembly and evolution of primitive membraneless compartments.