Observing the Birth of a Nanoplasma

The high-energy and high-intensity pulses available from x-ray free-electron lasers (XFELs) are leading to new studies of the structure of nanoscale objects such as proteins. But researchers also need to understand the interactions between x rays and matter in order to properly interpret such experiments. Now Yoshiaki Kumagai, of Tohoku University in Japan, and colleagues have revealed the earliest steps in the creation of a so-called nanoplasma, which appears when a powerful x-ray pulse hits a cluster of a few thousand atoms.