Deep engineering is a research field and methodological approach focused on the design, analysis, and implementation of technological systems that leverage fundamental physical principles, particularly those operating at the nuclear or sub-atomic level and involving core natural processes like fusion and fission. It investigates the practical application of deep scientific understanding to create complex, controlled systems, characterized by the integration of cutting-edge fundamental science with advanced systems engineering, often under extreme conditions and high energy densities. Its significance lies in enabling transformative technological capabilities, such as sustainable high-density energy generation, by mastering and applying the most profound forces and processes in nature.