Birgit Lugrin (maiden name Birgit Endrass) is a professor for media informatics at the University of Wurzburg, Germany. Since her first contact with a socially interactive agent (the Greta agent) in 2003, she has been fascinated about the research area. Ten years later, she received the prestigious IFAAMAS Victor Lesser Distinguished Dissertation Award and the research award from Augsburg University for her doctoral thesis titled "Cultural Diversity for Virtual Characters." Today she could not be happier about the chance to co-edit this handbook and work with all the great researchers who have contributed to make this happen. Catherine Pelachaud is Director of research at CNRS in the ISIR Laboratory, Sorbonne University. She received her PhD in Computer Graphics at the University of Pennsylvania, Philadelphia, PA, USA, in 1991. She participated in the elaboration of the first embodied conversation agent system, Gesture-Jack, with Justine Cassell, Norman Badler, and Mark Steedman when she was a post-doctoral researcher at the University of Pennsylvania. With her research team, she has been developing an interactive virtual agent platform, Greta, that can display emotional and communicative behaviors. David Traum is the Director for Natural Language Research at the Institute for Creative Technologies (ICT) and Research Professor in the Department of Computer Science at the University of Southern California (USC). He leads the Natural Language Dialogue Group at ICT. Traum's research focuses on dialogue communication between humans and artificial agents. He has engaged in theoretical, implementational, and empirical approaches to the problem, studying human–human natural language and multimodal dialogue, as well as building a number of dialogue systems to communicate with human users. Traum earned his PhD in Computer Science at the University of Rochester in 1994.