33 specimens illustrating the relationship between colour and constitution in organic substances, 1900-1913. The series was curated between 1911 and 1913 for a display at the Science Museum, London, to demonstrate how chemical structure could be manipulated to produce dyes of a different colour. Most of these specimens were prepared by Frances Micklethwait and Gilbert Thomas Morgan at Imperial College London (Royal College of Sciences), between 1904 and 1913.

One area of Morgan and Micklethwait's research included diazo compounds, which were used to make artficial dyes.