The Guest Editors of Communications Chemistry's Atomically precise nanochemistry Collection discuss the importance of atomic precision in nanochemistry research, and highlight some of the field's most pressing challenges. N anomaterials produced by various approaches usually display dispersity in their shapes, sizes, and compositions, which play a significant role in determining their physicochemical properties. Synthesizing nanomaterials with atomic precision is therefore of importance. With well-defined structure-property relationships, it is possible to achieve reliable and programmable performances in a diverse range of applications of interest. The need for atomic precision becomes imperative when the characteristic size of the nanomaterials decreases to a few nanometers or even the sub-nanometer scale. In this size range similar to molecules, every atom counts. Upon configurational changes, or addition or removal of a single atom, properties may vary significantly and in unpredictable ways. Properties are affected by the spatial distribution of elements and by nanomaterial size. Because every atom counts towards defining properties, it is critically important to develop robust synthetic approaches, such that "nanochemistry" may efficiently manufacture nanoscale materials with atomic precision. Recent efforts in nanochemistry have allowed the synthesis of a range of atomically precise nanomaterials, including metal nanoclusters, semiconductor magicsize clusters, polyoxometalate clusters, carbon-based nanostructures, and inorganic nanocrystals. These nanomaterials achieve a level of structural precision similar to that of molecules. Ligand-protected metal nanoclusters of atomic precision are the class of nanomaterial that this Collection features most