The evolution of wireless communication from 1G to 5G has significantly enhanced data rates, connectivity, and reliability, yet the demands of beyond-5G and sixth-generation (6G) networks necessitate more advanced solutions. Future systems must simultaneously support ultra-reliable low-latency communication, enhanced mobile broadband, and massive machine-type communication, while addressing the dual challenges of spectrum scarcity and sustainable energy management. Non-orthogonal multiple access (NOMA) has emerged as a promising technique by enabling multiple users to share the same resource block, thereby improving spectral efficiency and large-scale connectivity. Complementing this, simultaneous wireless information and power transfer (SWIPT) allows energy harvesting from radio-frequency signals alongside reliable data transmission, enabling energy-efficient communication for large-scale deployments. In addition, reconfigurable intelligent surfaces (RIS) provide an innovative means of reconfiguring the wireless propagation environment through programmable reflecting elements, thereby improving coverage, energy efficiency, and interference management. This chapter presents the principles and mathematical foundations of NOMA, explores SWIPT-enabled cooperative strategies, and highlights the integration of RIS with NOMA to achieve scalable, energy-efficient, and adaptive heterogeneous cellular networks. The joint utilization of NOMA, SWIPT, and RIS is identified as a cornerstone for future wireless systems, ensuring both massive connectivity and sustainable energy-efficient communication.