What foundational theories serve as cornerstones in chemical engineering? From the fundamental principles of thermodynamics, elucidating energy transformations and equilibrium states, to fluid mechanics, unveiling the behaviors of fluids in motion, these theories underpin the discipline's core. Material balance principles, outlining the conservation of mass in chemical processes, and transport phenomena, governing the movement of mass, momentum, and energy, further shape its framework. Additionally, reaction kinetics, delineating the rates of chemical reactions, and process control theories, facilitating efficient operation and optimization, contribute significantly. How do these theories interplay in designing processes, optimizing efficiency, and ensuring sustainability in chemical engineering applications?