Young children are a bundle of paradoxes. Infants might spend most hours sleeping, but intuitively know that objects will fall if not supported, and that people reach for things they like rather than dislike. A toddler might speak two languages without much explicit instruction, but struggle to use a toothbrush until they turn four. How can we explain these paradoxes? Let us take a look at case studies and methods from cognitive development research to unravel the contents and mechanisms of human intelligence. We will begin by exploring the intuitive knowledge that infants have before their first birthday. Next, we will discover how preschoolers learn through play and exploration. Finally, we will describe some challenges that researchers face in conducting experiments with infants and young children and talk about how some new technologies can help address these issues. Ultimately, this lecture will showcase the techniques and insights from psychological research to answer the big question: What makes us intelligent? We hope to leave audience members with a fresh perspective on just how rich “common sense” reasoning can be, and perhaps some new activities to try with the young children in their lives.