RB1 and retinoblastoma: Based on live imaging data of early tumors from patients’ eyes, the inner nuclear layer of the retina seemed to be the origin [11], but based on experiments, it has been suggested that human retinoblastoma arise from differentiating cones as it was found that retinoblastoma cells exhibit multiple elements of the cone precursor signaling circuitry and depend on this circuitry for their proliferation, survival [12], and RB1 knockdown-induced human cone precursor proliferation [13].