Fig. 1. Macromolecular components and the resulting four types of droplets.

a Molecular structures of pentameric constructs of SH3 domains (S) and proline-rich motifs (P), lysozyme (L), heparin (H), and polylysine (pK), rendered by electrostatic surfaces (blue and red: positive and negative electrostatic potentials, respectively). L is fully folded, P, H, and pK are fully disordered, and S contains both folded domains and disordered linkers. b pK:H, P:H, S:P, and S:L droplets settled on a coverslip, visualized by the fluorescence of either FITC-labeled H (green) or Alexa 594-labeled S (red), reproduced from ref. ²⁶. The growing tallness of droplets in the series gives a crude indication of a modest increase in interfacial tension from pK:H to S:L.