A brand-new class of photoreceptors has been identified in the past 20a: intrinsically photosensitive retinal ganglion cells(ipRGC). With melanopsin as its photopigment, ipRGCs transmit light signals to non-imaging brain regions like the suprachiasmatic nucleus(SCN)and the olivary pretectal nucleus(OPN)to regulate circadian photoentrainment and pupillary light reflex; a small portion of the signals are projected to brain imaging regions like the dorsal lateral geniculate nucleus(dLGN)and superior colliculus(SC), to participate in imaging vision. There are six different ipRGC subtypes(M1～M6), each with its own morphological and physiological characteristics. In addition to receiving signaling inputs from the rods and cones, ipRGCs also regulate retinal signals through chemical and electrical synapses and play important roles in visual signaling and visual development. It has been discovered that ipRGCs are implicated in several systemic and ocular illnesses. Overall, various aspects of ipRGC are reviewed including the discovery, general physiological properties, signaling, and the relationship with disease in this work.