Over two centuries ago, the keen observations of physiologist Jan Evangelista Purkyně laid the groundwork for understanding a fascinating quirk of human perception. Purkyně noticed a peculiar transformation in the appearance of red flowers, which seemed to undergo a dramatic shift in hue from vibrant carmine during sunny days to a sombre, muted tone at nighttime. This phenomenon, now referred to as the Purkinje effect, sheds light on how colours appear differently depending on the level of ambient light.