Crackling noise, characterized by discrete, impulsive events spanning a broad range of sizes, is observed in various physical systems, including earthquakes, paper crumpling, and magnetic materials. This phenomenon is studied using simple models and the renormalization group to understand its universality and self-similarity. The renormalization group helps in understanding how the effective evolution laws of a system change at different length scales, leading to scaling behaviors and universal scaling functions. The paper discusses the development of models for crackling noise, the challenges in making quantitative comparisons between theory and experiments, and the potential applications of understanding this phenomenon. Despite progress, the field remains challenging, with many systems yet to be fully explained by the current theories.Crackling noise, characterized by discrete, impulsive events spanning a broad range of sizes, is observed in various physical systems, including earthquakes, paper crumpling, and magnetic materials. This phenomenon is studied using simple models and the renormalization group to understand its universality and self-similarity. The renormalization group helps in understanding how the effective evolution laws of a system change at different length scales, leading to scaling behaviors and universal scaling functions. The paper discusses the development of models for crackling noise, the challenges in making quantitative comparisons between theory and experiments, and the potential applications of understanding this phenomenon. Despite progress, the field remains challenging, with many systems yet to be fully explained by the current theories.