Thousands of years ago the Greek learn how to grind clear glass into curved shapes. They use these lenses to focus sunlight to strat scared sample fires. Later people forgets how to make lenses.
In the middle ages people in Europe use glass containers full of water to magnify threads while making lace. Someone gets the idea to grind a curved lenses and make a magnifying glass. Today, lenses focus light for glasses, telescopes, cameras, microscopes.
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