Lesson 1 from the classic paper "The Development of Embodied Cognition: Six Lessons from Babies" is `Be Multimodal'. This talks explores how recent work in the computer vision literature on audio-visual self-supervised learning addresses this challenge. The aim is to learn audio and visual representations and capabilities directly from the audio-visual data stream of a video (without providing any manual supervision of the data) - much as an infant could learn from the correspondence and synchronization between what they see and hear. It is shown that a neural network that simply learns to synchronize audio and visual streams is able to localize the faces that are speaking (active speaker detection) and objects that sound.