Small modular reactors (SMRs) are emerging as a major next step in nuclear energy, promising lower upfront costs, faster construction, modular deployment, and improved safety compared with conventional large reactors. This article explains how SMRs work, explores key reactor technologies such as light-water, molten salt, and fast reactors, and examines the biggest opportunities and risks shaping their future in clean energy, industrial decarbonization, and reliable power generation.