Circular resonators are promising candidates for a wide range of applications, ranging from optical communication systems through basic research involving highly confined fields and strong photon–atom interactions to biochemical and rotation sensing. The main characteristics of circular resonators are the Q factor, the free spectral range (FSR), and the modal volume, where the last two are primarily determined by the resonator radius. The total internal reflection (TIR) mechanism used for guidance in “conventional” resonators couples these attributes and limits the ability to realize compact devices exhibiting large FSR, small modal volume, and high Q. Recently, a new class of annular resonator, based on a single defect surrounded by radial Bragg reflectors, has been proposed and analyzed. The radial Bragg confinement decouples the modal volume from the Q and paves the way for the realization of compact, low-loss resonators. These properties as well as the unique mode profile of these circular Bragg nanoresonators (CBNRs) and nanolasers (CBNLs) make the devices within this class an excellent tool to realize nanometer scale semiconductor lasers and ultrasensitive detectors, as well as to study nonlinear optics.