This paper introduces the main notions that are addressed in this special issue, namely evidentiality, modality, and grammaticalization. It defines each notion and briefly synthesizes the literature. It also presents some of the controversies which surround the ideas that prevail in these research fields. Crosslinguistic examples illustrate the main evidential and modal categories, and clarify why the two domains are both distinct and related. The paper then sketches the main pathways of grammaticalization of modal and evidential markers as they have been documented in typological work. Finally, it introduces the contributions to this special issue, highlights the new insights, and discusses what remains to be investigated on the links between evidentiality, modality, and grammaticalization.