Aggregation-induced emission (AIE) has become a significant area of research since its discovery in 2001. This review summarizes recent advances in AIE research, focusing on the structure-property relationships of AIE systems, their photophysical mechanisms, and technological applications. AIE systems exhibit enhanced light emission when aggregated, unlike conventional aggregation-caused quenching (ACQ) systems, where emission decreases with aggregation. The key difference lies in the restriction of intramolecular rotations (RIR) in AIE systems, which blocks non-radiative decay pathways and enables radiative emission. Examples include hexaphenylsilole (HPS), which becomes highly emissive in aggregates due to restricted rotation. Other AIE systems, such as 8,8a-dihydrocyclopenta[a]indene derivatives and 1,4-distyrylbenzene derivatives, also show AIE behavior through structural and conformational changes. Heteroatom-containing luminogens, like pyridinium salts and phospholes, exhibit tunable emission colors and enhanced stability. Polymeric AIE luminogens, such as poly(1-phenyl-1-alkyne)s and carborane-based polymers, show aggregation-enhanced emission (AEE) and are useful for optoelectronic and biological applications. Organometallic AIE systems, including platinum and iridium complexes, exhibit phosphorescence in aggregates due to RIR processes. The review highlights the importance of structural design in developing efficient AIE luminogens and their potential for high-tech applications. The AIE effect offers a new approach to light emission, enabling the development of novel materials and technologies.Aggregation-induced emission (AIE) has become a significant area of research since its discovery in 2001. This review summarizes recent advances in AIE research, focusing on the structure-property relationships of AIE systems, their photophysical mechanisms, and technological applications. AIE systems exhibit enhanced light emission when aggregated, unlike conventional aggregation-caused quenching (ACQ) systems, where emission decreases with aggregation. The key difference lies in the restriction of intramolecular rotations (RIR) in AIE systems, which blocks non-radiative decay pathways and enables radiative emission. Examples include hexaphenylsilole (HPS), which becomes highly emissive in aggregates due to restricted rotation. Other AIE systems, such as 8,8a-dihydrocyclopenta[a]indene derivatives and 1,4-distyrylbenzene derivatives, also show AIE behavior through structural and conformational changes. Heteroatom-containing luminogens, like pyridinium salts and phospholes, exhibit tunable emission colors and enhanced stability. Polymeric AIE luminogens, such as poly(1-phenyl-1-alkyne)s and carborane-based polymers, show aggregation-enhanced emission (AEE) and are useful for optoelectronic and biological applications. Organometallic AIE systems, including platinum and iridium complexes, exhibit phosphorescence in aggregates due to RIR processes. The review highlights the importance of structural design in developing efficient AIE luminogens and their potential for high-tech applications. The AIE effect offers a new approach to light emission, enabling the development of novel materials and technologies.