The primitives of phonological theory – whether we call them features, elements, gestures, or by some other name – represent the smallest units in phonology and stand in some relation to phonetic reality. At least this much most phonologists would agree on; but once we begin to ask further questions concerning the precise nature of the primitives, we find a significant divergence of views. What kind of primitives are there? How are they structured? And what is their phonetic exponence? This chapter presents an overview of our current understanding of the nature of phonological primitives, and of the key issues that play a role in the debate on this topic. We do this as a way of framing the following contributions of the book, which approach the topic of phonological primitives from different theoretical and experimental perspectives.