In the liverwort Marchantia polymorpha, male and female sexual branches exhibit a conspicuous morphological difference, yet the cell-level patterning processes governing the formation of this sexual dimorphism remain largely unknown. Cui et al. (on pp. 866-879) now disclose that the primordia of male and female sexual branches exhibit an overall similar morphology in early stages, yet they are already differentiated in terms of the spatial distribution patterns of cell division and elongation, as well as the disposition of germline precursors that subsequently develop into the sex-specific spatial arrangement of sperm- and egg-containing reproductive organs (gametangia).