Natural products and synthetic small molecules can be used to perturb, dissect and manipulate biological processes, thereby providing the basis for drug development. Over the past decades, the evolution of molecular biology protocols and microscopy techniques has made it possible to visually detect proteins in living systems with valuable spatiotemporal resolution, in which dynamic topological information has proved to be insightful. By contrast, although small molecules have become essential for biological studies, general methods to track them in cells remain underexplored. In this Review, we discuss how bioorthogonal chemistry, and click chemistry in particular, can be exploited to label and visualize almost any biologically active small molecule in cells and tissues. We review recent developments, highlighting cases in which visualizing small molecules has provided crucial mechanistic insights. This methodology is facile to implement, is versatile and is illuminating.

天然产物和合成的小分子可用于扰动，解剖和操纵生物过程，从而为药物开发提供基础。在过去的几十年中，分子生物学协议和显微镜技术的发展使人们有可能以有价值的时空分辨率目视检测生命系统中的蛋白质，其中动态拓扑信息已被证明是有见地的。相比之下，尽管小分子已成为生物学研究必不可少的方法，但在细胞中追踪小分子的一般方法仍未得到充分研究。在这篇综述中，我们讨论了如何利用生物正交化学，尤其是点击化学，来标记和可视化细胞和组织中几乎任何具有生物活性的小分子。我们回顾了最近的发展，突出显示小分子可视化提供了关键的机械洞察力的案例。该方法易于实施，用途广泛且具有启发性。