This review article explores the strong coupling between surface plasmon polaritons (SPPs) and quantum emitters, such as excitons in J-aggregates, dye molecules, and quantum dots. The authors provide a comprehensive overview of the background physics of SPPs, including their dispersion relations and near-field characteristics. They discuss the historical development of strong coupling experiments and recent advancements, highlighting the importance of nano-fabrication techniques in achieving this regime. The article delves into three theoretical frameworks—classical, semi-classical, and fully quantum mechanical—to explain the strong coupling phenomenon. It also examines the implications of strong coupling for various applications, such as quantum information processing and chemical reactions. The review concludes with a perspective on the future of this emerging field, emphasizing its potential to expand into other areas of science.This review article explores the strong coupling between surface plasmon polaritons (SPPs) and quantum emitters, such as excitons in J-aggregates, dye molecules, and quantum dots. The authors provide a comprehensive overview of the background physics of SPPs, including their dispersion relations and near-field characteristics. They discuss the historical development of strong coupling experiments and recent advancements, highlighting the importance of nano-fabrication techniques in achieving this regime. The article delves into three theoretical frameworks—classical, semi-classical, and fully quantum mechanical—to explain the strong coupling phenomenon. It also examines the implications of strong coupling for various applications, such as quantum information processing and chemical reactions. The review concludes with a perspective on the future of this emerging field, emphasizing its potential to expand into other areas of science.