This book is designed for undergraduates and graduates pursuing studies in materials science, nanoscience and nanotechnology, and solid-state physics. It brings bulk silicon and nanomaterial graphene face-to-face in a comprehensive exploration of their distinct physical properties and transformative potential. By examining how these materials behave at different scales, it bridges the gap between fundamental science and potential of cutting-edge applications. The text begins with fundamental principles of silicon and graphene in thermal equilibrium. It proceeds further to cover lattice defects, thermal, electrical, and optical properties of these materials. It highlights how the physics of materials undergo a transformation when one moves from the study of three dimension structure of silicon to the two-dimensional structure of graphene. Each chapter incorporates updated insights on graphene's evolution over time. Silicon's limitations are critically examined while graphene's rise as a game-changer is showcased, thus emphasizing its capacity to revolutionize various industries.