This paper has two purposes: (1) to explain briefly in terms of Piaget's theory why relationships are fundamental for constructivist teachers; and (2) to show how constructivist teachers can think about relationships in classroom activities. In a nutshell, the message is that the process by which children are constructing their intelligence, personality, and social and moral selves, including the emotional aspects can be observed. This process involves early forms (foreshadowing) of the same kinds of relationships in infancy and early childhood that Piaget describes as characteristic of his last stage in cognitive development--the formal operational stage. The educational significance of this isomorphism (sameness in general form at all stages) is that it gives the strongest rationale for a constructivist approach to education--that is, that development of formal operations from 11 to 12 years depends on the construction of relationships in early childhood. Thus, Piaget shows the continuity of development, and the logic of adolescents and adults can be traced back to the constructions of babies and pre-school children. The rationale for emphasizing the construction of relationships in education is that it is basically by constructing relationships that children elaborate their knowledge and develop their intelligence. For Piaget, "Intelligence is the construction of relationships". To understand what Piaget meant by the construction of relationships, it is necessary to refer to their context in his theory. In this article, the author discusses briefly the notions of assimilation and accommodation, and meaning and meaning implications. Examples that illustrate some of the activities included in a constructivist curriculum inspired by Piaget's research and theory, and indicate how constructivist teachers think about relationships while planning activities are presented.