This chapter introduces the formulas as a source genre and in particular the manuscript and formula collection that occupies the center of this study: Paris, BNF ms. lat. 2123 and the formulas from Flavigny. It also introduces the concepts “early medieval Europe” and “early medieval laity,” in order to frame the questions that shape the book. The chapter briefly describes how the category “lay” even came to exist; that is, how and when a category “clerical” distilled out of late and post-Roman Christian society and came by the Carolingian period to separate clergy and monks from laypeople. From there it moves into what we know about how lay people lived their lives in post-Roman and early medieval Frankish Europe, and what remains unknown that makes it worth writing a new book about. The chapter then sets the Flavigny formulas in the context of the other Carolingian formula collections, presenting it (and them) as a gateway into a different world. Finally, the chapter briefly outlines the steps we need to open the gate and to understand what we see on the other side, and the topics we will explore when we get there.