part of compound eye photoreceptor development R3/R4 cell differentiation R3/R4 development The process whose specific outcome is the progression of the R3 and R4 pair of photoreceptors in the eye over time, from their formation to the mature structures. R3 and R4 are paired photoreceptors that contribute to the outer rhabdomeres. An example of this process is found in Drosophila melanogaster. GO:0048057 biological_process