Stimulated scattering in supermode microcavities, such as Raman or Brillouin lasers, has shown unprecedented merit for precision measurements by exploiting the beat note in their lasing spectra. This beat note corresponds to the energy splitting of supermodes and is highly sensitive to any external perturbations. However, a pivotal question has puzzled the researchers for two decades: are these supermode microcavity lasers single or dual modes? Now, a research team led by Professor Xiao Yunfeng at Peking University has revealed the lasing dynamics of a stimulated scattering laser in a supermode microcavity, and experimentally demonstrated its single-mode nature. This work has been published online in PNAS.