Ligand-protected metal nanoclusters (NCs) are ultrasmall particles (<3 nm) that represent the molecular state of metal materials. Owing to their molecule-like structure — particularly their atomic precision and protein-like hierarchy — metal NCs feature numerous useful molecule-like properties, including discrete energy levels, strong luminescence, intrinsic magnetism and programmable catalytic activity. In this Review, by regarding metal NCs as metallic analogues of organic molecules, we summarize methodological and mechanistic advances in their precise synthesis at the molecular and atomic levels. We first decipher cluster structure based on a protein-like hierarchical scheme and discuss synthetic strategies that realize molecular monodispersity in these clusters. We resolve formation mechanisms of metal NCs at the molecular level, aiming to establish step-by-step reaction maps reminiscent of total synthesis routes of organic molecules. We then examine approaches to customize the composition and morphology of the metal core, metal–ligand interface and ligand shell at the atom level. This Review concludes with our perspectives on the future development of atomic precision chemistry in both metal NCs and other inorganic nanomaterials.

配体保护的金属纳米团簇 （NCs） 是代表金属材料分子状态的超小颗粒 （<3 nm）。由于其分子状结构——特别是它们的原子精度和蛋白质样层次结构——金属 NC 具有许多有用的分子状特性，包括离散能级、强发光、本征磁性和可编程催化活性。在这篇综述中，通过将金属 NCs 视为有机分子的金属类似物，我们总结了它们在分子和原子水平上精确合成的方法和机制进展。我们首先基于类蛋白质分层方案破译簇结构，并讨论在这些簇中实现分子单分散性的合成策略。我们在分子水平上解析了金属 NCs 的形成机制，旨在建立让人想起有机分子总合成路线的逐步反应图。然后，我们研究了在原子水平上定制金属核、金属-配体界面和配体壳的组成和形态的方法。本文总结了我们对金属 NC 和其他无机纳米材料中原子精密化学未来发展的看法。