We begin this Chapter by stating a few principles on what early childhood professionals and developmental psychologists believe on how babies and young children develop cognitively: 1. Young children construct their knowledge through their interactions with objects and people, and are not passive recipients of knowledge. They are motivated to achieve new means for new ends. 2. Young children are primed to explore and discover their environment, and deduce the regularities or principles of how things operate and relate to one another, with qualitative changes in different stages of development. 3. Social interactions and rich, warm relations with caregivers are the indispensable crucible in which all domains of development occur. In a nutshell, we think children are able and competent, curious and resourceful, and possess the neural mechanisms to relate to their physical and social environment from day one; but they must have caring, interactive adults to propel and scaffold their development. In this Chapter, we begin our review with motor and perceptual development in infancy and the early years, as perceptual motor integration forms the earliest building blocks of cognitive development. We will also examine Piaget's constructivist theory, and Vygotsky with his emphases on social structures as necessary prerequisites to cognitive growth and development. We then consider social cognition, theory of mind and moral development in early childhood.