Abstract: The debate on the cell of origin of human retinoblastoma lasted for more than one century.In the recent issue of "cell",David Cobrinik's group shows that L/M cone precursors are the most likely answer as they have an intrinsic circuitry,including murine double minute 2 (MDM2),N-myc,the nuclear receptors retinoid X receptor and thyroxine receptor 2,making them extremely sensitive to transformation following retinoblastoma gene inactivation.