As they look around them, infants routinely observe many different types of physical events: for example, they may see a parent step out of view behind a door (occlusion event), stack cups and dishes (support event), or hit a ball (collision event). How well do infants understand such events? Traditionally, researchers believed that infants understood very little of the physical world. With the advent of more sensitive methodologies, however, investigators have come to realize that even young infants are capable of sophisticated reasoning about physical events. The talk will be divided into two parts. In the first, we will examine what knowledge young infants possess about various types of physical events and how this knowledge develops over time. In the second part, we will explore how infants attain their physical knowledge. In this context, we will consider several recent accounts of the innate and experiential factors that contribute to infants' acquisition of knowledge about physical events.