We've been looking at colours across the spectrum, but what about those invisible to the human eye? Infra-red and ultra-violet were discovered within a year of each other (1800 and 1801) by William Herschel and Johann Ritter respectively. The scientific uses are huge, with a bewildering range of applications. Humans, being the supercilious types we are, assume that we have the best vision. Is that really true? It's more a case of adaptation. Bees, for example, can "see" pollen on flowers. We can't, but we don't really need to. The "pits" that pit vipers have are infra-red sensory organs. Lots of animals see the world in a very different way to us. Wildlife documentaries can show us all kinds of new things thanks to nighttime cameras. We can learn about what goes on in space as well as our own planet. We can use infra-red to help preserve art. What's even better is that we are probably not even close to discovering all of the uses of light beyond the spectrum.