In contemporary settings, the term, Shīʿism, is primarily used to refer to three extant Shīʿite sects, Zaydism, Ismāʿīlism and Twelverism. However, a careful review of earlier historical, biographical and heresiographical sources will reveal the existence of a diverse mosaic of early Shīʿite sects and schools that once flourished and later became extinct due to various socio-political reasons. Later Twelver and, to a lesser extent, Zaydī and Ismāʿīlī hegemony in the Shīʿite realm has undermined and overshadowed the legacy of many earlier Shīʿite schools and movements that often disagreed with the extant Shīʿite schools on a variety of subjects. Furthermore, some of the extinct schools should not necessarily be regarded as independent sects; rather, they may prove to be multifactedly related to the extant Shīʿite sects. This concise book seeks to provide a brief visualized overview of the divergence of Shīʿite sects with respect to the imamate, one of the core subjects of Shīʿism as a whole. It includes a set of diagrams that outline the divergence (and occasional convergence) of early Shīʿite schools with respect to the imamate. Attempting to thoroughly summarize and visualize multifaceted and intricate theological disputes in flow diagrams is a difficult (and perhaps impossible) task, and this work accordingly is bound by various limitations. The diagrams in this book are not meant to be the be-all-and-end-all of research on this topic. To the contrary, they are intended to be mere gateways into further research and inquiry on the history, development and relationships of early Shīʿite schools.