10 Inventions That Were Discovered Completely by Accident

In 1928, bacteriologist Alexander Fleming came back from vacation to a messy lab and a petri dish he’d left out. A blob of mold had grown on it — and everywhere the mold touched, the bacteria had died.

Most people would have rinsed the dish and moved on. Fleming looked closer, and the world got its first true antibiotic. It’s fair to say that one dirty dish has saved more lives than almost any invention in history.

In 1945 an engineer named Percy Spencer was standing near a magnetron — a device for radar — when he noticed the chocolate bar in his pocket had melted. Curious, he tried popcorn next. It popped.

Within a couple of years that stray observation became the microwave oven. The first models were nearly six feet tall; it took decades to shrink one down to fit on your kitchen counter.

A 3M scientist named Spencer Silver was trying to make a strong adhesive and instead came up with a weak one that stuck lightly and peeled off clean. For years nobody knew what to do with it.

Then a colleague, tired of his paper bookmarks falling out of his church hymnal, coated them with the stuff. The Post-it note was born — a hit product built entirely on a glue that had failed at its one job.

After a walk in the woods in the 1940s, Swiss engineer George de Mestral got curious about the burrs stuck to his socks and his dog’s fur. Under a microscope he saw tiny hooks that grabbed onto anything with a loop.

He spent years turning that idea into hooks-and-loops you could sew onto anything. If you’ve ever fastened a sneaker or a jacket with that satisfying rrrip, you have a walk in the woods to thank.

Around 1903 a French chemist knocked a glass flask off his bench — but instead of shattering, it just cracked and held together. It had held a coating that dried into a thin film inside.

That accident led to laminated safety glass, the kind that holds together instead of spraying everywhere. It’s in your car windshield right now, quietly doing its job.

In 1905 an eleven-year-old named Frank Epperson left a cup of flavored soda powder and water on his porch overnight, with the stirring stick still in it. San Francisco had a rare cold snap, and by morning it was frozen solid.

He pulled it out by the stick and had himself a treat. Years later he patented it. Not bad for a kid who just forgot to bring his drink inside.

In 1895 the physicist Wilhelm Röntgen was experimenting with a vacuum tube when he noticed a screen across the room glowing, even though the tube was covered. Some invisible ray was passing straight through solid objects.

One of the first images he made was of his wife’s hand, bones and wedding ring clear as day. She is said to have gasped, “I have seen my death.” Medicine was never the same.

During World War II, a researcher named Harry Coover was trying to make clear plastic gunsights when he kept producing a substance that stuck to absolutely everything. Annoyed, he set it aside as a failure.

Years later he realized that sticking to everything was the whole point. Super glue went on sale in the 1950s, and it’s been welding our broken mugs and eyeglasses back together ever since.

Play-Doh started life as a putty for cleaning coal soot off wallpaper. When home heating changed and the cleaner stopped selling, the company was nearly sunk.

Then someone noticed schoolchildren using the stuff for arts and crafts. They pulled the soap out, added color and a smell you’d know anywhere, and a doomed cleaning product became one of the best-selling toys of all time.

In 1943 a naval engineer named Richard James was working on springs to steady equipment on ships when he knocked one off a shelf. Instead of clattering to the floor, it “walked” down in a graceful, tumbling arc.

His wife Betty saw a toy, gave it a name, and the Slinky went on to sell by the hundreds of millions. If you ever sent one down the stairs, you know the appeal never really wears off.