How a tiny lean becomes a big one

Hold up your two hands. Mirror images, but they never fit on top of each other. Many molecules of life come in a left-hand and a right-hand version, and life almost always picks just one. This week the 2026 Nobel Prize in Chemistry went to Henri Kagan (95) and Kenso Soai (76) for showing how a tiny lean can grow, all by itself, into a landslide. Soai heard the news at the supermarket.

In 1953 Charles Frank imagined a molecule that copies itself and beats its mirror twin. In 1986 Kagan showed that a small lean in a chemical helper can become a big one. Soai's team found a reaction whose product helps make more of itself, like sourdough starter making more starter. In 1995 it turned a near-tie of 51 to 49 into about 93 to 7. In 2003 it worked with no handed ingredient at all, and when another team tested it 54 times, it came out 27 left and 27 right: a coin flip decided by the molecules themselves.

It doesn't prove how life began. But it shows how a whole world could end up one-handed, and it gives chemists, including those who make medicines, new ways to build just the hand they need.