We are starting to crack the mystery of how lightning and thunderstorms work

Imagine lying on a green hill watching the clouds go by on a beautiful day. The clouds you're probably thinking of are cumulous clouds, the ones that resemble fluffy balls of cotton wool. They seem innocent enough. But they can grow into the more formidable cumulonimbus, the storm cloud. These are the monsters that produce thunder and lightning. They are powerful, destructive and intensely mysterious. They may also be getting a lot more common, which makes understanding their workings—and their effects on the human world, including how we construct buildings or power lines—more important than ever.