This lecture covers the concept of natural system of units, focusing on Newton and Maxwell theories in CGS units. It explains the fundamental equations and relationships between physical quantities, such as force, energy, and momentum, in a simplified and coherent manner. The lecture delves into the significance of different units and their interplay in the context of quantum mechanics, shedding light on the creation of particles and the logical possibilities within the field. Additionally, it explores the untenable aspects of certain physical quantities and the compulsory nature of specific relationships, providing a comprehensive overview of the foundational principles governing the natural system of units.