These observations, wrote Einstein, were "the origin of the next great theoretical advance, which had to await, over a hundred years, the coming of Thomas Young." INSIGHTS In 1931, Albert Einstein wrote a foreword to the fourth edition of Isaac Newton's 1704 Opticks, which described Newton's experiments with, and explanations of, phenomena associated with light, including his observations of the colors of thin films. In 2023, the 250th anniversary of Young's birth, the chief lesson of his life for scientists is surely how Young made his greatest discovery, the double-slit experiment. [Extracted from the article]