Nuclear reactions induced by photons play a vital role for very different aspects of basic research and applications in physics. They are a key ingredient for the synthesis of nuclei in the Universe and provide, due to the selectivity and the model-independence of the reaction mechanism, an extremely valuable probe for researchers. The penetrability of photons in the MeV energy range makes them, in addition, an ideal tool for meeting various societal challenges. The last two decades saw a rapid development of advanced photon sources and detection methods for photonuclear reaction products. Bremsstrahlung and quasi-monoenergetic photon beams with unprecedented intensity and quality combined with state-of-the-art detector technology paved the way for new scientific discoveries and technological applications.

This review focuses on a comprehensive overview of the most important developments since the turn of the millennium restricted to the energy range between atomic and hadronic degrees of freedom. This includes a description of the formalism of photonuclear reactions below and above the particle-separation threshold. The most important techniques used to generate photon beams in the MeV energy range are presented along with selected facilities and instrumentation for diagnostics and for the analysis of photonuclear reactions. The power of photons to probe the atomic nucleus is exemplified in a number of selected examples from fundamental and applied science. New developments, facilities, and ideas promise a vivid future for photonuclear physics.

光子引发的核反应在物理学基础研究和应用的不同方面起着至关重要的作用。它们是宇宙中原子核合成的关键成分，由于反应机制的选择性和模型独立性，它们为研究人员提供了极有价值的探索。此外，MeV 能量范围内光子的穿透性使它们成为应对各种社会挑战的理想工具。在过去的二十年里，先进的光子源和光核反应产物的检测方法得到了快速发展。具有前所未有的强度和质量的轫致辐射和准单能光子束与最先进的探测器技术相结合，为新的科学发现和技术应用铺平了道路。

这篇综述的重点是全面概述自千禧年以来最重要的发展，仅限于原子和强子自由度之间的能量范围。这包括对低于和高于粒子分离阈值的光核反应形式的描述。介绍了用于产生 MeV 能量范围内的光子束的最重要技术以及用于诊断和光核反应分析的选定设施和仪器。光子探测原子核的能力在基础科学和应用科学的许多选定示例中得到了例证。新的发展、设施和想法为光核物理学带来了光明的未来。