How do we know that no two snowflakes are alike?
Wilson Bentley (1865-1931) was a self-educated farmer in Vermont who in his teen years became interested in ice crystals and began examining them under a microscope. He attached a camera to his microscope and developed a technique for photographing snowflakes before they melted or sublimated—a technique which is still used today. His photographs have become world renowned, being exhibited by museums, published in Scientific American and National Geographic, and spawning a colloquialism that is as ubiquitous as the snow itself.
"Under the microscope, I found that snowflakes were miracles of beauty; and it seemed a shame that this beauty should not be seen and appreciated by others. Every crystal was a masterpiece of design and no one design was ever repeated. When a snowflake melted, that design was forever lost. Just that much beauty was gone, without leaving any record behind."
--Wilson "Snowflake" Bentley 1925