Résumé : The developmental researcher is relating to different tools to understand how newborns, infants and children perceive the visual world. In this paper, we will describe the preference and habituation paradigms, the eye tracking technique, behavioural measures, event-related potentials, positron emission tomography and functional magnetic resonance imaging. We will mention how to use these tools when the researcher's interest is focused on faces. Finally, we will show that the choice of a unique or of several tools highly depends on the experimenter's research interests and the participants' age.