For years, fluid physicists have confounded over Rayleigh–Taylor Instability’s mixing layers. Rayleigh–Taylor (R.T.) instability is a well-known hydrodynamic phenomenon with applications in various scientific and engineering fields. This study comprehensively investigates R.T. instability using advanced Computational Fluid Dynamics simulations. The study begins with a detailed review of the theoretical background and the equations governing the R.T. instability. Numerical simulations are carried out to study the fundamental aspects of R.T. instability, including the influence of different physical parameters such as density ratios, Atwood numbers, and surface perturbations on the instability growth rates and characteristic wavelengths. Furthermore, the study delves into the implications of R.T. instability in various engineering scenarios, including mixing in multiphase flows, fuel sloshing in aerospace vehicles and plasma-fluid interaction in stars. The outcomes of this research will deepen our understanding of R.T. instability and pave the way for developing advanced predictive models and engineering strategies to control and exploit this phenomenon for practical applications. The knowledge gained from this study holds immense potential for enhancing the efficiency, safety, and performance of a wide range of fluid systems and processes.