The discovery of sequential organization in the mid-to-late 1960s more or less coincided with the emergence of conversation analysis as a field. Others had pointed to the existence of paired actions, but Sacks and Schegloff discovered the normative order or logic undergirding such paired actions or adjacency pairs. The relatedness of the two turns in an adjacency pair has both a prospective and retrospective dimension. The occurrence of a first pair part creates a slot for a specific second pair part. At the same time, a second pair part displays its speaker’s understanding of the first to which it responds. Adjacency pairs allow then for a framework of understanding that is constructed and sustained on a turn-by-turn basis. The response to the first pair part that promotes the accomplishment of activity is, typically, the preferred one. The features of dispreferred second pair parts play a role in minimizing the chance that such a response will, in fact, ever be articulated. Sequences can be much more complex than composed of only two turns. Clearly, there are a great many different kinds of distinctive sequence types.