This study presents the first experimental demonstration of PT-symmetry breaking in optical resonator systems using two directly coupled on-chip optical whispering-gallery-mode (WGM) microtoroid silica resonators. One resonator provides optical gain via Erbium (Er³⁺) ions, while the other exhibits passive loss. The coupling strength between the resonators is controlled by adjusting their distance using nanopositioning stages. The system exhibits reciprocal behavior in the linear regime and transitions to nonreciprocal behavior in the PT symmetry-breaking phase due to enhanced nonlinearity. The results demonstrate strong nonreciprocal light transmission in the nonlinear regime with a low power threshold, providing direct experimental clarification of nonreciprocity in PT-symmetric systems. The PT-symmetric system consists of two WGM resonators, with one active (gain) and one passive (loss). The system's behavior is analyzed by varying the coupling strength and gain-to-loss ratio. The experiments show that the system transitions from a symmetric to a broken-symmetry phase, where the eigenfrequencies become complex. In the broken-symmetry phase, the system exhibits nonreciprocal light transmission, with light passing in only one direction. This nonreciprocal behavior is attributed to the enhanced nonlinearity in the broken-symmetry phase, which is induced by strong field localization due to PT-symmetry breaking. The study also demonstrates that PT-symmetry alone is not sufficient for nonreciprocal light transmission; operation in the nonlinear regime is necessary. The results show that in the linear regime, the system is reciprocal regardless of whether PT-symmetry is broken or unbroken. The experiments provide the first experimental demonstration of nonreciprocal light transmission in a PT-symmetric system without the use of magneto-optic effects, operating in the nonlinear regime and broken-symmetry phase. The results have significant implications for the development of synthetic optical systems and on-chip manipulation of light propagation. The study extends the concept of PT-symmetric optics from centimeter- and meter-scale structures to micro-scale structures, and from waveguides to microresonators. The findings contribute to the field by demonstrating the first PT-symmetric optical microresonators with clear PT symmetry breaking, providing experimental verification that PT-symmetry alone is not sufficient for nonreciprocal behavior, and demonstrating nonreciprocal light transmission in a PT-symmetric system. The results also suggest that coupled WGM microresonators can be used to explore resonance effects in PT-symmetric optical systems, aiding the development of CPA lasers and on-chip synthetic structures.This study presents the first experimental demonstration of PT-symmetry breaking in optical resonator systems using two directly coupled on-chip optical whispering-gallery-mode (WGM) microtoroid silica resonators. One resonator provides optical gain via Erbium (Er³⁺) ions, while the other exhibits passive loss. The coupling strength between the resonators is controlled by adjusting their distance using nanopositioning stages. The system exhibits reciprocal behavior in the linear regime and transitions to nonreciprocal behavior in the PT symmetry-breaking phase due to enhanced nonlinearity. The results demonstrate strong nonreciprocal light transmission in the nonlinear regime with a low power threshold, providing direct experimental clarification of nonreciprocity in PT-symmetric systems. The PT-symmetric system consists of two WGM resonators, with one active (gain) and one passive (loss). The system's behavior is analyzed by varying the coupling strength and gain-to-loss ratio. The experiments show that the system transitions from a symmetric to a broken-symmetry phase, where the eigenfrequencies become complex. In the broken-symmetry phase, the system exhibits nonreciprocal light transmission, with light passing in only one direction. This nonreciprocal behavior is attributed to the enhanced nonlinearity in the broken-symmetry phase, which is induced by strong field localization due to PT-symmetry breaking. The study also demonstrates that PT-symmetry alone is not sufficient for nonreciprocal light transmission; operation in the nonlinear regime is necessary. The results show that in the linear regime, the system is reciprocal regardless of whether PT-symmetry is broken or unbroken. The experiments provide the first experimental demonstration of nonreciprocal light transmission in a PT-symmetric system without the use of magneto-optic effects, operating in the nonlinear regime and broken-symmetry phase. The results have significant implications for the development of synthetic optical systems and on-chip manipulation of light propagation. The study extends the concept of PT-symmetric optics from centimeter- and meter-scale structures to micro-scale structures, and from waveguides to microresonators. The findings contribute to the field by demonstrating the first PT-symmetric optical microresonators with clear PT symmetry breaking, providing experimental verification that PT-symmetry alone is not sufficient for nonreciprocal behavior, and demonstrating nonreciprocal light transmission in a PT-symmetric system. The results also suggest that coupled WGM microresonators can be used to explore resonance effects in PT-symmetric optical systems, aiding the development of CPA lasers and on-chip synthetic structures.