In 1665, an experiment was carried out to investigate the nature of colour. Newton darkened a room and made a hole in the window shutter, so that a narrow ray of sunlight was allowed to enter the room. A glass prism was taken and placed in the ray of light. The result was that the prism split the light into a band of colours like a rainbow - a spectrum. When he placed a second prism upside down in front of the first prism, it recombined the different colours of the spectrum into White light. At last, someone had scientifically demonstrated the relationship between light and colour.