Coacervates as phase-separated droplets in biology: (a) A mammalian cell with various types of membraneless organelles, (b) free exchange of proteins and small molecules in one such coacervate-based compartment due to a lack of membrane, (c) example of liquid nature of phase-separated droplets of small heat shock protein B2 (HspB2) in the nucleus of HEK293 cells, (d) synthetic coacervate droplets made from short peptide derivatives, (e) upon fusion and settling, coacervates can form macroscopic dense liquid phases. The position of the interface is highlighted with an arrow.