Primitive membraneless compartments as a window into the earliest cells.

What did the first cells on Earth look like? This is an unanswered mystery investigated by researchers in the origins of life field. While at some point cells must have developed membranes, genetic components, and catalytic cycles and catalysts, when the earliest cells developed these is not clear. One system which could shed light into the structure and function of the first cells on Earth is membraneless compartments generated from phase separation, perhaps before or as a precursor to the advent of membrane-bound compartmentalization. Here, we briefly comment on two prebiotically relevant membraneless compartment systems: coacervates and polyester microdroplets. This discussion seeks to highlight the current understanding of these systems and to pose unanswered questions as a challenge to the field at large.