Think you know how phase change works? You might need to rethink that. Researchers at Princeton, Peking University and New York University say the process is a lot more complex than previously known. "This research shows that phase changes can follow multiple pathways, which is counter to what we've previously known," explains Mark Tuckerman, a professor of chemistry and applied mathematics at NYU and one of the study's co-authors. "This means the simple theories about phase transitions that we teach in classes are just not right."