Probably this, taken from Wikipedia: > To help keep his methods confidential he apparently intentionally encouraged others to think grinding was his primary or

Probably this, taken from Wikipedia: > To help keep his methods confidential he apparently intentionally encouraged others to think grinding was his primary or only lens construction method. https://en.wikipedia.org/wiki/Antonie_van_Leeuwenhoek#Microscopic_study https://en.wikipedia.org/wiki/Antonie_van_Leeuwenhoek#Micros... The linked paragraph describes the lens creation method and it appears to not be simple or obvious. > By placing the middle of a small rod of soda lime glass in a hot flame, one can pull the hot section apart to create two long whiskers of glass. Then, by reinserting the end of one whisker into the flame, a very small, high-quality glass lens is created. I think I need to see this in a video, I have no idea what he did from just that description... In any case, it lead to him having a monopoly, apparently never revealing his production method for his advanced lenses (he also used ground lenses, but they were not as good): > By the end of the seventeenth century, van Leeuwenhoek had a virtual monopoly on microscopic study and discovery. His contemporary Robert Hooke, an early microscope pioneer, bemoaned that the field had come to rest entirely on one man's shoulders.[28] He was visited over the years by many notable individuals, such as the Russian Tsar Peter the Great. To the disappointment of his guests, van Leeuwenhoek refused to reveal the cutting-edge microscopes he relied on for his discoveries, instead showing visitors a collection of average-quality lenses. By the way, of the nine (of twenty-five) single-lens microscopes he produced: "Those that have survived are capable of magnification up to 275 times"