An intrinsically photosensitive retinal ganglion cell (ipRGC) as it would appear if you looked at a mouse's retina through the pupil. The white arrows point to the many different types of cells ...

He found that these cells have an extremely low pigment (melanopsin) content--only about 104 molecules per cell in mouse, compared to about 108 rhodopsin molecules in a mouse rod, despite the much ...