Penicillin, Post-it notes, and microwaves were all discovered by accident. These happy accidents changed the world forever.

Medical Accidents

1. Penicillin was discovered in 1928 when Alexander Fleming returned from vacation to find mold growing on a petri dish of staphylococcus bacteria. The mold was killing the bacteria around it. This accidental discovery has saved an estimated 200 million lives.

2. X-rays were discovered in 1895 when Wilhelm Roentgen noticed that a fluorescent screen in his lab glowed even when his cathode ray tube was covered with black cardboard. He had discovered invisible rays that could pass through solid matter.

3. Viagra was originally developed as a heart medication to treat angina. During clinical trials, patients reported an unexpected side effect. The drug now generates billions in annual revenue as a treatment for erectile dysfunction.

Kitchen Accidents

4. The microwave oven was invented when engineer Percy Spencer noticed a chocolate bar melted in his pocket while working with radar equipment in 1945. He realized microwaves from the radar set were cooking the candy.

5. Coca-Cola was created by pharmacist John Pemberton as a medicinal syrup containing coca leaf extract and kola nut. It was originally marketed as a cure for headaches, fatigue, and morphine addiction.

6. Saccharin, the first artificial sweetener, was discovered when chemist Constantin Fahlberg forgot to wash his hands after work and noticed his dinner tasted unusually sweet. It was 300 times sweeter than sugar.

Office Accidents

7. Post-it Notes were invented because a 3M scientist, Spencer Silver, was trying to create a super-strong adhesive but instead created a weak, repositionable one. The product sat unused for years until a colleague used it to mark pages in his hymnal.

8. Super Glue was discovered twice. First in 1942 when scientists were trying to create clear plastic gun sights for WWII —the formula was rejected as too sticky. It was rediscovered in 1951 and marketed as an adhesive.

9. The pacemaker was invented when engineer Wilson Greatbatch accidentally installed the wrong resistor into a heart rhythm recording device. The circuit produced electrical pulses mimicking the hearts natural rhythm.

Scientific Serendipity

10. Velcro was invented in 1941 when Swiss engineer George de Mestral examined the burrs stuck to his dogs fur after a walk. He saw tiny hooks on the burrs and created a two-sided fastener.

11. Teflon was discovered in 1938 by a chemist trying to create a new refrigerant. He found a mysterious slippery substance in a gas cylinder that was resistant to heat, chemicals, and sticking.

12. The Slinky was created when naval engineer Richard James knocked a tension spring off his desk and watched it walk end-over-end across the floor. Over 300 million have been sold since 1945.

13. Safety glass was discovered when chemist Edouard Benedictus dropped a glass flask coated with cellulose nitrate. Instead of shattering, it cracked but held its shape, leading to laminated safety glass used in car windshields.

14. The Big Bang theory received crucial support from an accident —in 1964, Arno Penzias and Robert Wilson detected persistent microwave noise from their radio antenna, which turned out to be cosmic microwave background radiation, the afterglow of the Big Bang.