Coloring the heartbeat

In the 17th Century two giants of science, Isaac Newton and Robert Hooke, were both trying to understand how the wings of butterflies and peacocks, which are made of the same material as our fingernails and hair, could colors of such brilliant quality. They both came to the same conclusion, the color was a result of tiny structures on the wing, structures so small that they could not observe it themselves but had deduced must exist.