Your mom may have packed up your lunch-break PB&J, but she couldn’t have done it without the help of Margaret Knight. Living in 19th century America, Knight was something we don’t often hear about in that age: a prolific woman inventor. She designed a kind of window sash, a numbering machine, and even a form of internal combustion engine. When an ironsmith she had hired to build a prototype for one invention tried to steal her patent, she wasn’t afraid to take him to court and reclaim her intellectual property. But Knight’s most lasting innovation can still be seen in grocery stores and school cafeterias. She invented a machine that folded and glued flat-bottomed, brown paper bags.