The existence of “adjacency pairs” is one of the major discoveries by the founders of conversation analysis. In the present paper, I revisit the adjacency pair, and in particular the underpinning concept of conditional relevance (Schegloff, 1968), through examining the analyses presented in the articles in the March 2009 special issue that focus on the multimodality of interaction. In addition to the fact that these articles are indicative of the usability of conditional relevance in analyzing various multimodal interactional settings, I will discuss the fact that conditional relevance can become effective not only upon the completion of
the first pair part of an adjacency pair (FPP) but also before the production of
the FPP. Furthermore, through analyzing child-caregiver interactions from my own data, where adjacency pair operates as the machinery for organizing a complex participation framework of interactional moments involving a young child and a preverbal infant, I will argue that the adjacency pair is the primordial engine for organizing human interaction.