Continuous-flow photochemistry in microreactors has gained significant attention due to its advantages over batch processing, including reduced reaction times, higher selectivity, improved scalability, and enhanced safety. This review provides an updated overview of photochemical transformations in continuous-flow reactors, covering applications in organic synthesis, material science, and water treatment. The advantages of continuous-flow photochemistry are highlighted, and a detailed comparison with batch processing is presented. The review discusses the fundamentals of flow photochemistry, including nine key reasons for adopting photoflow technology. These reasons include improved irradiation of the reaction mixture, reliable scale-up, improved reaction selectivity and reproducibility, fast mixing, fast heat exchange, multiphase chemistry, multistep reaction sequences, immobilized catalysts, and increased operational safety. The review also covers the materials used for photomicroreactor fabrication, such as glass and polymer-based materials, and the selection of appropriate light sources for photochemical applications. In organic synthesis, continuous-flow photochemistry has been applied to various reactions, including photocycloadditions, photoisomerizations, cyclizations, and singlet oxygen-mediated oxidations. The review highlights the use of different photocatalysts, such as ruthenium, iridium, copper, cobalt, and titanium dioxide, in these reactions. In material science, continuous-flow photochemistry has been used for polymer synthesis and nanoparticle production. In water treatment, continuous-flow photochemistry has been applied for water purification and the removal of contaminants using TiO₂ and photo-Fenton processes. The review concludes that continuous-flow photochemistry offers significant advantages over batch processing, including improved reaction efficiency, scalability, and safety. It also emphasizes the importance of further research and development in this field to fully realize the potential of continuous-flow photochemistry in various applications.Continuous-flow photochemistry in microreactors has gained significant attention due to its advantages over batch processing, including reduced reaction times, higher selectivity, improved scalability, and enhanced safety. This review provides an updated overview of photochemical transformations in continuous-flow reactors, covering applications in organic synthesis, material science, and water treatment. The advantages of continuous-flow photochemistry are highlighted, and a detailed comparison with batch processing is presented. The review discusses the fundamentals of flow photochemistry, including nine key reasons for adopting photoflow technology. These reasons include improved irradiation of the reaction mixture, reliable scale-up, improved reaction selectivity and reproducibility, fast mixing, fast heat exchange, multiphase chemistry, multistep reaction sequences, immobilized catalysts, and increased operational safety. The review also covers the materials used for photomicroreactor fabrication, such as glass and polymer-based materials, and the selection of appropriate light sources for photochemical applications. In organic synthesis, continuous-flow photochemistry has been applied to various reactions, including photocycloadditions, photoisomerizations, cyclizations, and singlet oxygen-mediated oxidations. The review highlights the use of different photocatalysts, such as ruthenium, iridium, copper, cobalt, and titanium dioxide, in these reactions. In material science, continuous-flow photochemistry has been used for polymer synthesis and nanoparticle production. In water treatment, continuous-flow photochemistry has been applied for water purification and the removal of contaminants using TiO₂ and photo-Fenton processes. The review concludes that continuous-flow photochemistry offers significant advantages over batch processing, including improved reaction efficiency, scalability, and safety. It also emphasizes the importance of further research and development in this field to fully realize the potential of continuous-flow photochemistry in various applications.