A broken seal of a lab cuvette led an American researcher in the Netherlands to the origin of many an inexplicable result: the weather. Or the humidity, because this determines the water concentration in oils used as solvents, which was previously thought to be negligible. Lone water molecules in oil aren’t just spectators, they firmly direct supramolecular processes. This outcome means that a lot of previous research has to be re-examined, but also that chemists get a new, cheap and powerful tool.