(a) Two windows of exposure to 1 μM RA were tested in combination with slight modifications to the culture media in CB-iPSC6.2-derived RCs. RA treatment in W7–W14 led to low levels of rod opsin expression in the distal part of photoreceptor cells as observed in the original culture conditions, except for some RCs that showed few cells with rod opsin expression in the cell bodies at W21. In contrast, RCs treated during W10–W14 showed dispersed cells with strong rod opsin expression in their cell bodies already at W17, and forming large patches at W21. We did not observe significant differences associated with modifications of the culture media after RA treatment or presence of fetal bovine serum/Taurine from W5. Similar results were observed in three independent experiments, five RCs per treatment per time window. (b–g) When KA.1- and IMR90-4-derived RCs were subjected to RA treatment in W10–W14, induction of rod opsin expression was also observed, although less efficiently than in CB-iPSC6.2-derived RCs (3 independent experiments, 8–22 RCs per cell line). Scale bars, 20 μm.