With remarkable ease, young children acquire significant insight into mental states, their experiences, psychological processes in themselves and others, and the natural world. It is a challenge to developmental theory to understand how they do so. The contributors to this special issue highlight how children's powerfully inductive mental capacities are aided by the conceptual catalysts of conversation, especially with mature partners. Conversation contributes to conceptual growth through the linguistic structures that scaffold developing knowledge (especially of complex and intangible influences) and permit its sharing; through the encounter with divergent perspectives and a more knowledgeable partner; through its influence on representations of past, present, and anticipated events; and as a medium of cultural transmission. Parents' conversational discourse provokes conceptual growth in developing minds, and children also contribute significantly to conversational quality, which is affected by the quality of the parent-child relationship, the emotional climate of the home, and other influences. This article introduces the special issue by profiling these issues and identifying central themes for future research.