More than two decades after the first demonstration, gallium nitride (GaN) wide bandgap (WBG) semiconductors are revolutionizing an increasing number of applications from power electronics, RF communications, to light-emitting diode (LED) lighting, photovoltaic solar cells, integrated nanophotonics, and more. For example, GaN WBG power devices technology is presently making a significant impact on energy efficiency and on transforming the electric grid from a passive one to an actively controlled physical-cyber system. This impact is not only economic (over $40B in annual electricity savings), or environmental (equivalent of 300 coal fired power plants worth of energy), but critical for new device concepts and system architectures which will radically change the way people generate, distribute, and consume electricity every day. At the heart of all these exciting applications is the GaN WBG materials, the unique electronic and optical properties of which have enabled and will continue to enable new paradigms in electronic and photonic technologies with hitherto unachievable capabilities and innovative functionalities. In this talk, I will review our progress on GaN materials research, and discuss their applications in kV-class power transistors (supported by APRAe) and high temperature solar cells (supported by NASA). For future outlook, I will further present and argue the possibilities of new WBG devices based on AlN and diamond materials (supported by DTRA and AFOSR), and emerging UV/visible GaN integrated photonics for biochemical sensing, nonlinear optics, and quantum photonics applications (supported by ARO and SFAz).