''Granular matter'' is encountered everywhere in our surroundings (sand, salt, rice, powders, ...) and in industrial processes. Despite this, the modelling of the statics and the dynamics of this form of matter remains, until today, a challenge. In this seminar, I will try to give a flavour of some recent models which have been proposed to describe the flow of granular matter (''avalanches''). I will also present some predictions on the course of avalanches. Rather than enumerate (alleged) certainties, the talk will hopefully give a sense of a science which is still in the making.