Dandelions in UV light. Coloured photograph of dandelion flowers (Taraxacum officinale) showing areas that absorb (red) and reflect (pale areas) ultraviolet (UV) light. These bull's-eye patterns are known as 'nectar guides' and help to attract pollinating insects, which can see UV light. Humans are unable to see these patterns. This image was taken using a digital camera adapted to filter and detect UV light. The resulting monochrome image was coloured on computer. UV light is outside the visible spectrum and does not have a true colour.