In this chapter, we focus on the development of explanatory abilities in French children attending nursery school and grade school. Even if young children are unable to produce written explanatory texts, there is nothing to stop them from formulating oral explanations. It is the “why” type of explanation that we intend to examine here and, more specifi cally, the way it develops with age. Furthermore, since speech acts are multimodal, children’s explanatory verbal productions are frequently accompanied by bodily movements (hand and head gestures, facial expressions, changes of posture). The observation of gesture associated with speech provides data of considerable interest to anyone in the fi eld of discourse development and the evolution of abstract thought.