In chemical engineering, theories serve as the cornerstone for understanding and optimizing complex processes. These theories draw upon principles from chemistry, physics, and mathematics to elucidate the behavior of materials and chemical reactions in various systems. From fundamental concepts like thermodynamics and kinetics to advanced computational models, they guide the design of processes across industries, from pharmaceuticals to energy production. How do these theories drive innovation and efficiency in chemical engineering? What methodologies and interdisciplinary approaches underpin their development, enabling the creation of sustainable and economically viable processes?