Imagine a child explaining a conservation judgment by saying, That one's wider, while indicating the height of a glass with his hand. Now, consider an adult saying, She chased him, while brandishing an imaginary umbrella in her hands. In both of these examples, information different from that conveyed by speech is communicated by movements of the hands. These movements of the hands that co-occur with speech - gestures - are the subject of this volume of the "New Directions for Child Development" series. Although gesture has always been considered relevant to talk, it has usually been seen as a stream separate from speech, one that can reflect the attitudes and feelings of speakers, but that is not centrally involved in language. It was not until recently that gesture became a legitimate interest of language researches. The chapters herein focus on the spontaneous gestures that accompany speech, especially the speech of children. Together they confirm that gesture is a robust and integral part of communication that can provide unique insights into the mind.