Atomic motion captured in 4-D for the first time

Transitions from one state of matter to another—such as freezing, melting or evaporation—start with a process called "nucleation," in which tiny clusters of atoms or molecules (called "nuclei") begin to coalesce. Nucleation plays a critical role in circumstances as diverse as the formation of clouds and the onset of neurodegenerative disease. A UCLA-led team has gained a never-before-seen view of nucleation—capturing how the atoms rearrange at 4-D atomic resolution (that is, in three dimensions of space and across time).