Behind the complex phenomenon of the phylogenetic development of tool use and its potential causal implication for higher forms of cognition, there are important 'lower level' aspects of cognition that highlight how tool use plays a causal role in shaping both spatial and bodily representations, and this is the focus of this chapter. First, it offers a definition of the word tool and in particular of what can be called tool use in our perspective, for operational purposes. Second, it considers the causal role that tool use plays in producing changes in space perception and body representation. Third, it discusses the challenges tool use presents for the sensorimotor system of the human and non-human primate brain.