This paper proposes digital hardware building block concept for emulating power system networks on field-programmable gate arrays (FPGAs) in real time. Basic hardware emulation building blocks (HEBBs) for machines, transmission lines, nonlinear elements, and loads are presented to demonstrate how real-time simulation can be achieved for realistic power systems. All of the hardware modules were developed using the VHDL language for portability and extensibility. Employing multiple FPGAs, a large-scale power system consisting of 1260 three-phase buses is modeled in detail in real time to show both electromagnetic transients and electromechanical dynamics in the system. The advantage of HEBB-based modeling is that the design and development of new technologies can be accelerated by utilizing massive real-time digital simulators capable of modeling multi-scale and multi-domain dynamics.