The Gordon and Betty Moore Foundation’s Symbiosis in Aquatic Systems Initiative and the Simons Foundation Life Sciences Division are jointly soliciting proposals for research on the origin of the eukaryotic cell. In addition to seeking researchers who currently work in these areas, we hope to identify scientists and engineers who have not previously worked on these topics and who would bring novel perspectives, methods and technologies to these important areas of science. The deadline for submitting a proposal is September 30, 2019.