Hermann von Helmholtz took optics toward the physiology of perception. He developed and formalized Young's trichromatic theory, postulating that the human eye has three types of receptors sensitive to different wavelengths, whose combination produces the entire range of perceived colors. His Handbuch der Physiologischen Optik (1856–1867) founded physiological optics as an independent discipline. In the Wikinventia chain, Helmholtz is the node where the history of light branches: one branch continues toward wave physics and the laser; the other advances toward technical imaging and computer vision.