A pulse of light sent a metal-organic framework into a hidden electronic state in just 30 femtoseconds. Combining ultrafast laser spectroscopy with theoretical calculations allowed them to identify the transient electronic state and clarify its role in the rapid transition. “We found that the photoinduced hidden state forms within 30 fs through a previously unknown intermediate electronic state,” says Ishikawa. Those changes indicated that the hidden photoinduced state had formed. Together, the changing bond pattern and atomic movement carried the material into the photoinduced hidden state.