IT was observed many years ago that the crystallization of amorphous selenium is promoted and accelerated by illumination1,2. I rediscovered this in the summer of 1941 and succeeded in producing true photographic images by means of this effect, using the initial product of selenium manufacture, namely, aluminium or steel disks covered with a film of selenium, as photosensitive plates. To do this, the mirror-like surface of the selenium must be polished with a soft material, such as tissue paper. The disk is then placed on a metal plate, preheated at 90–95° C, and an image, preferably a diapositive, projected on the surface of the selenium. During exposure, 'self-development' takes place and in 1–2 minutes a somewhat faint but in other respects perfect image will appear. The photographic process is then complete and the disk can be removed from the hot plate.