History is full of men and women who have devoted countless hours to turning their ideas into physical properties. Thomas Edison had ideas about improving incandescent lighting, and he worked hard until he'd come up with a longer-lasting light bulb. And good for him! (He's why you're able to read this right now.) But there are just as many moments in our past where men and women have devoted those hours to realizing a dream only to see that dream crushed by the pragmatic demands of reality, then to realize that they've accidentally come up with something of equal or greater importance. Our lives depend on these accidental inventions more than we might know, and our world and economy are certainly in their debt. If you've ever cured your illness or nuked a TV dinner, you're living proof of the happiness of accidental discoveries.

1. Penicillin: Your relatives survived long enough to have you all because a Scottish scientist got lazy a hundred years ago. Alexander Fleming mistakenly left open a petri dish containing a sample of Staphylococcus bacteria, which ordinarily would qualify him as a poor technician. On that day in 1928, though, he got lucky: a blue-green mold had grown onto the dish, and Fleming noticed that the bacterial growth stopped at the mold area. He figured out that the mold was holding back the bacteria. He reworked a pure culture of the mold and discovered that it was a Penicillium mold, and our term "penicillin" comes from Fleming's term for the antibiotic molecule the mold produces. By 1930, penicillin was being used to cure patients of infection. Mass production kicked in in the 1940s, and the 20th century got a lot safer.
2. Microwave ovens: Microwaves: the single man's best friend. If it can be processed, reheated, or transported in a cardboard sleeve, it can be brought to piping hot life in a microwave oven. But the magical device that's saved many a college freshman's life almost wasn't invented. In 1945, American engineer Percy Spencer was conducting experiments with magnetrons for Raytheon, trying to develop better radar technology, when he noticed that the radar had melted a chocolate bar he had in his pocket. He repeated the exposure with popcorn and an egg, and soon enough noted that he could cook foods by piping microwave power into a metal box to create an electromagnetic field. The device was patented in October 1945, and the first commercial microwave appeared in 1947, though at almost 6 feet tall, it wasn't exactly portable. Soon enough, compact technology and TV dinners would ensure that this accidental discovery would make its way into every house in America.
3. Viagra: We haven't solved world hunger, but we can give old dudes an assist in the bedroom. Progress! Sildenafil citrate, better known as Viagra, was originally developed as a treatment for high blood pressure and angina pectoris. The effects on angina were negligible, but scientists noticed that the pill induced long-lasting erections. Before you could say "Let's make a creepy commercial," Pfizer was marketing the little blue pill to men dealing with erectile dysfunction. The drug was OK'd for use by the DFA in 1998. It's now a billion-dollar business.
4. Velcro: Swiss engineer Georges de Mestral probably never dreamed he'd come up with a fastener beloved by astronauts and young children alike, or that he'd owe his success to his dog. In 1941, de Mestral took his dog hunting in the Alps. When he returned home, he noticed that multiple cockleburs were stuck in his dog's fur. Curious, bored, and Swiss, the engineer examined the burrs under a microscope and discovered they used tiny hooks to catch the fur and transport themselves. With that, the idea of a hook-and-loop fastener was born, though it was years of trial and error before de Mestral finalized the design and patented it in 1955. The fastener known as Velcro got a huge PR boost when it was adopted by NASA as a means of securing spacesuits without zippers, after which it was pretty much no holds barred. Shoes, bags, jackets: the stuff went everywhere. Here's hoping that dog got a treat.
5. Super glue: "Super glue" is just the generic catch-all title we use for brands like SuperGlue and Krazy Glue, and they're in turn just fancy names for Cyanoacrylate, the fast-acting adhesives that seem to hold most of the world together. They were discovered by fluke, too. In 1942, a pair of doctors at Kodak Laboratories were trying to come up with a transparent plastic to be used on gun sights, since this was the middle of World War II and every spare scrap of resources we had was being devoted to the war effort. They kept messing up the formula and coming up with extremely sticky stuff, instead. A few years later, Kodak sold the formula to Loctite, which went on to make Super Bonder. The work the scientists did for gun sights was helpful to the military, but their mistake turned out to be a boon for consumers for years.
6. Saccharin: A pioneer in artificial sweeteners, saccharin owes its existence to scientists working with coal tar derivatives. In 1878, chemist Constantin Fahlberg was working at Johns Hopkins University on those coal tar derivatives and went home to have dinner. He noticed a sweet taste on his hand, and he reasoned that it had come from the substances he'd been working with, namely benzoic sulfimide. A few years later, Fahlberg patented the sweetener and dubbed it saccharin. Despite initial commercial success, though, it was the supply shortages of the Great War that sent demand for saccharin skyrocketing. Since then, it's been a staple of business, particularly restaurants, where you can find packets of the stuff on every table.
7. Corn flakes: Corn flakes were, in short, discovered by hardcore religious conservatives who were scared that spicy foods would make them have wanton sex. Backing up a bit: Dr. John Kellogg, a Seventh-day Adventist and superintendent of the Battle Creek Sanitarium, liked feeding his patients bland foods, fearing that anything more daring than graham crackers would incite horrible lust in their loins. Kellogg and his younger brother one day accidentally left out some cooked wheat, which went stale. They put it through rollers anyway, but instead of sheets of dough, they were left with flakes, which they toasted up and served to their guests. The flakes were a big hit, and the recipe was patented in 1896. Kellogg started selling the flakes to mass audiences not long after, and thus began the lengthy life of one of the most popular breakfast cereals and cereal companies in the world. All because he forgot to cover the wheat.
8. Slinky: Proof positive that kids in the mid-20th century had really low standards for entertainment, the Slinky was nothing more than a loose spring sold in a box. In 1943, a mechanical engineer named Richard James was working in the naval shipyards of Philadelphia to fashion springs that would keep instruments steady during storms and rough seas. He accidentally knocked one of the springs off a high shelf and saw it "walk" from surface to surface until it hit the floor. Not a stupid man, James tweaked the design and soon started impressing neighborhood families with the toy. Patents and mass production followed quickly, and by the 1950s, the thing was absolutely everywhere. The infamous 1960s jingle become one of the longest-running history, burned so deeply into our collective subconscious that parodies followed even decades later.
9. Teflon: More than a few food-related inventions have been total luck, and Teflon is no exception. Teflon -- the DuPont brand name for polytetrafluoroethylene, a synthetic fluoropolymer -- is a life-saving pan coating that's kept food chunks out of cookware (and vice versa) since the 1940s. The substance was discovered by accident in 1938 when a chemical engineer named Roy Plunkett was trying to come up with a new refrigerant. The nature of the experiments is fairly technical, but the bottom line is that he noticed additional weight appearing in test bottles being used in the gaseous research. Sawing one open, he discovered it had become coated with a slippery white surface. This was the fluorinated plastic that would become known as Teflon. By 1948, DuPont was churning out 900 tons of the stuff every year. Just about every meal you've ever prepared or been served owes its life to Teflon.
10. Play-Doh: Play-Doh was invented on purpose, but not for the reasons you'd think. The clay-like material, largely composed of flour, water, and salt, was originally sold as a wallpaper cleaner by Cincinnati's Kutol Products in the 1930s. A local classroom started letting kids use it as a modeling compound, since it could easily be broken down and reshaped or stored for later use. Kutol, rightly sensing a trend, changed the formula and started marketing the compound as Play-Doh in the 1950s. They formed Rainbow Crafts and started selling the stuff in bigger quantities, earning a patent in 1965. General Mills bought them out shortly thereafter, and the product continued its meteoric rise to fame. What child hasn't handled the stuff by now? It's arguably one of the biggest of all accidental discoveries, since it existed before its modern use was realized. All it took was one little push.