Visible light photocatalysis has emerged as a promising approach for chemical synthesis, leveraging the ability of transition metal complexes to absorb visible light and drive reactions. This review highlights the mechanisms and applications of visible light photocatalysis, emphasizing its potential to generate reactive intermediates such as radicals, amine radical cations, and triplet alkenes. The use of visible light allows for the efficient conversion of solar energy into chemical potential, enabling the synthesis of complex organic molecules. Transition metal complexes like ruthenium and iridium are particularly effective in this process, as they can absorb visible light and generate excited states that facilitate electron transfer or energy transfer reactions. These reactions can lead to the formation of highly reactive intermediates, which are then used to construct complex molecular structures. The review also discusses various applications of visible light photocatalysis, including the synthesis of organic radicals, the activation of amines, and the generation of radical ions. The ability to control these reactions through visible light provides a sustainable and efficient method for chemical synthesis, with potential applications in materials science, chemical biology, and drug discovery. The development of visible light photocatalysis continues to expand the range of chemical transformations that can be achieved, offering a complementary strategy to traditional methods in organic synthesis.Visible light photocatalysis has emerged as a promising approach for chemical synthesis, leveraging the ability of transition metal complexes to absorb visible light and drive reactions. This review highlights the mechanisms and applications of visible light photocatalysis, emphasizing its potential to generate reactive intermediates such as radicals, amine radical cations, and triplet alkenes. The use of visible light allows for the efficient conversion of solar energy into chemical potential, enabling the synthesis of complex organic molecules. Transition metal complexes like ruthenium and iridium are particularly effective in this process, as they can absorb visible light and generate excited states that facilitate electron transfer or energy transfer reactions. These reactions can lead to the formation of highly reactive intermediates, which are then used to construct complex molecular structures. The review also discusses various applications of visible light photocatalysis, including the synthesis of organic radicals, the activation of amines, and the generation of radical ions. The ability to control these reactions through visible light provides a sustainable and efficient method for chemical synthesis, with potential applications in materials science, chemical biology, and drug discovery. The development of visible light photocatalysis continues to expand the range of chemical transformations that can be achieved, offering a complementary strategy to traditional methods in organic synthesis.