As well as being one of the Founding Fathers of the United States, Benjamin Franklin was also a man of science and an inventor. Many of his inventions are still with us today, most notably bifocals.
As with many inventions, bifocals came out of a pressing personal need. Franklin was getting on in life and, as is often the case with the aged, was starting to experience a notable deterioration in his eyesight.
Franklin, who was both short and long-sighted, used two pairs of spectacles, one for reading and the other for seeing at distances. As one can imagine, he found it incredibly tiresome and annoying to keep switching between two pairs of glasses.
So he came up with the brilliant idea of bifocals. He cut the lenses from each pair of glasses in half and remade them into a single lens. The top part of the lens would then be used for seeing distances, whereas the bottom part would be used for reading.
Bifocal technology today is of course much more advanced than it was in Franklin's day. But it was Franklin himself, motivated by a need to solve a very personal problem, who laid the groundwork for what would become an invention that, over centuries, has been of great benefit to millions of people the world over.