They say war is hell, and they're right. But even in the worst of human experiences, we can find the best of human innovation.

It was 100 years ago this week that the United States entered World War I. While the war resulted in the development of tools of warfare (poison gas, armored tanks, and fighter planes, for example), it also spurred the creation of useful inventions and innovations we still use today--some of which will really surprise you.

Here are 10 peacetime innovations that came out of the so-called "war to end all wars."

1. Zippers

How did they keep their jackets closed and their pants before zippers? Buttons, I suppose, and ties. The zipper wasn't technically invented during World War I, but it became mainstream during the conflict, when military suppliers suddenly had a massive need for flight jackets and other military clothing.

2. Drones

Inventors Elmer Sperry and Peter Hewitt, members of the Naval Consulting Board, built technology that enabled development of a remote controlled airplane--only 15 years after the first flight. They had about 100 successful test flights, but the war ended before their remote controlled aircraft--intended as a flying bomb--was put into production.

3. Industrial fertilizer

Obviously we've used fertilizer since ancient times, but two wartime German scientists found a way to turn nitrogen into ammonia, which now helps produce food for "one third of the population on Earth," according to one source. The Germans were actually using the process to create explosives; agricultural fertilizer was an ancillary use.

4. Sanitary napkins

New medical technology meant some wounded soldiers survived injuries that would have killed them in prior wars--one such advance was the development of absorbent surgical gauze. Red Cross nurses began using the gauze when they had their periods, which ultimately led to development and use of disposable pads after the war.

5. Daylight savings time

The idea of turning the clocks ahead to save sunlight had been around for a long time, but it was Germany that put it into practice a temporary wartime measure in 1916. Then the British followed, then the Americans, and now we can all eat dinner at sidewalk cafes after work in the summer.

6. Air traffic control

The first airplanes were basically cut off from the ground, meaning there was no practical way for pilots to communicate with anyone on land. The advent of the war led the U.S. Army to develop radiotelegraphs that could send messages from ground to air or even from one airplane to another.

7. Tea bags

The British love their tea, but it was the Germans who popularized the idea in World War I of packaging tea in small bags that could be dropped right into a pot of boiling water. (While an American company had invented the idea, it was the Germans who mass produced tea bags during the war.)

8. Triage

The word came from Napoleonic times, but the Royal Army Medical Corps put it into practice during the first World War, segmenting wounded soldiers into three categories: those who required immediate medical attention in order to live, those who were wounded but could be delayed care, and those who were unlikely to survive.

9. Kleenex

Much like the development of surgical gauze and menstrual pads, the advent of a cotton-like fabric that was stronger than cotton and could be produced cheaply enough to be disposable led to modern facial tissue. They first hit the market about a decade after the war.

10. Plastic surgery

Again, medical progress meant wounded soldiers could survive wounds that would have been fatal in earlier wars, but that often meant living with severe injuries. A New Zealand-born surgeon, Harold Gillies, came up with ways to graft skin, bones, and muscles--"paving the way for modern-day plastic surgery," as the Wall Street Journal put it.