A Z-contrast Scanning Transmission Electron Micrograph of several AlZr3 precipitates in an aluminum alloy. The apparently popcorn-shaped precipitates form at 375 degrees C and are responsible for increasing the strength of the alloy. Each precipitate is roughly 15 nanometers across. Image courtesy of Joerg Jinschek, Bill Reynolds, Vincent Caluori, Kristine Obusek, and Keith Knipling.