The light from a single molecule is like a lone voice in a vast choir. To hear it, you need not a microphone but a delicate instrument that catches each photon and notes its arrival time. That's exactly what researchers have built: it measures not only the brightness and color of the glow but also how often photons arrive in pairs — what's called second-order statistics.

The IDTBT molecule is a long chain of alternating units, like beads. When illuminated, it absorbs light and re-emits it. But not just anyhow: inside the chain, energy can hop from one unit to another, and if those hops are coordinated, photons come out not one by one but with a certain pattern. The instrument showed that in different parts of the spectrum (that is, for different colors of the glow) the pattern differs. And the picture changes between room temperature and cooling to cryogenic temperatures.

Why does this matter? In nature, there are molecules that transfer energy with almost no loss — for example, in plant photosynthesis. It's thought that quantum coherence helps energy reach its destination faster. The new method lets us peek into this process at the level of a single molecule without destroying it. So far, the results are just a hint, but already it's clear: the quantum life inside a molecule is richer than we thought.