Reportage in the Baby Lab in Geneva, devoted to language learning in babies. A researcher tests babies to determine how language learning works. Babies take part in two studies that test, on the one hand, the learning of new words and on the other, their capacity to categorise. The child is filmed while it listens to sounds and watches films, then the researcers analyse its behaviour, in particular thanks to a system of eye-tracking that allows eye movements to be recorded.