The paper reports the first experimental demonstration of parity-time (PT)-symmetry breaking in optical resonator systems using two directly coupled whispering-gallery-mode (WGM) microtoroid silica resonators. One resonator is optically pumped with Erbium (Er$^{3+}$) ions to provide gain, while the other exhibits passive loss. The coupling strength between the resonators is adjusted by nanopositioning stages. The authors observed reciprocal behavior in the linear regime and a transition to nonreciprocity in the PT symmetry-breaking phase due to enhanced nonlinearity. This work advances the field of synthetic optical systems, enabling on-chip manipulation and control of light propagation, and provides a direct experimental clarification of nonreciprocity in PT-symmetric systems. The results highlight the importance of both PT symmetry and nonlinear effects for achieving nonreciprocal light transmission.The paper reports the first experimental demonstration of parity-time (PT)-symmetry breaking in optical resonator systems using two directly coupled whispering-gallery-mode (WGM) microtoroid silica resonators. One resonator is optically pumped with Erbium (Er$^{3+}$) ions to provide gain, while the other exhibits passive loss. The coupling strength between the resonators is adjusted by nanopositioning stages. The authors observed reciprocal behavior in the linear regime and a transition to nonreciprocity in the PT symmetry-breaking phase due to enhanced nonlinearity. This work advances the field of synthetic optical systems, enabling on-chip manipulation and control of light propagation, and provides a direct experimental clarification of nonreciprocity in PT-symmetric systems. The results highlight the importance of both PT symmetry and nonlinear effects for achieving nonreciprocal light transmission.