Light-matter interactions are the fundamental basis for many phenomena and processes in optical devices. This talk will cover ultra-high-quality whispering-gallery-mode (WGM) optical microresonators which provide an unprecedented capability to trap light in a highly confined volume smaller than a strand of human hair. Light beams can travel around the boundary of a WGM resonator over 10^6 times, significantly enhancing light-matter interactions, creating the potential for a wealth of new scientific discoveries and technological breakthroughs. High-Q microresonators and microlasers have great potential for both fundamental science and engineering applications; the choices of materials for the photonic resonators enable various opportunities for different applications. Examples range from low-threshold lasers to parity-time-symmetric resonators and their application for sensing and nonreciprocal light transmission. Our recent exploration of fundamental physics, such as light-matter interactions around exceptional points (EPs) in high-quality WGM resonators, unravels innovative strategies to achieve a new generation of optical systems enabling unconventional control of light flow. Examples including loss engineering in a lasing system, directional lasing emission, and EPs enhanced sensing will be presented. I will conclude my talk with a new finding in EP-enhanced sensing that can expand this approach to a wide range of optical sensor systems. Our research discoveries just represent a glimpse of the potentials of photonic resonators; there are still many exciting opportunities by leveraging the enhanced light-matter interactions through resonant effects in the future.