An army marches on its stomach
Napoleon's army needed food that would not go off. Appert sealed food in glass bottles and heated them in boiling water. He did not know why it worked; bacteria were only discovered by Louis Pasteur half a century later.
How to open a can without a can opener
The first cans were thick, and soldiers opened them with a knife, a bayonet or a hammer. The can opener only appeared once cans became thinner. The classic opener with a cutting wheel caught on at the beginning of the 20th century.
Today
Canned food and home preserving are still a cheap way to keep food for years. Cans are also very easy to recycle.