Temporal dissipative solitons have been observed in a high-Q optical microresonator. These solitons are spontaneously generated when the pump laser is tuned through the effective zero detuning point of a high-Q resonance, leading to red-detuned pumping. This regime is fundamentally new in nonlinear microresonators and is stable without active feedback. The number of solitons can be controlled via pump laser detuning, and transitions between soliton states are associated with discontinuous steps in resonator transmission. The solitons correspond to low-noise optical frequency combs with smooth spectral envelopes, critical for applications in broadband spectroscopy, telecommunications, astronomy, and low phase-noise microwave generation. High-Q nonlinear optical microresonators, such as dielectric whispering gallery mode or ring-type resonators, have attracted significant attention. Frequency comb generation in these resonators has evolved into a research field. The comb lines are generated via cascaded four-wave mixing (FWM), resulting in hundreds of equidistant and coherent optical lines. The comb line spacing corresponds to the free-spectral range of the microresonator. These combs can perform at levels required for optical frequency metrology, but often suffer from significant noise and do not correspond to ultra-short pulses in the time domain. In strongly driven nonlinear microresonators, the intracavity field as a function of the pump laser detuning cannot be described by a Lorentzian shape. Instead, the resonance is asymmetrically shifted towards lower frequencies due to Kerr nonlinearity. This leads to bistable behavior, with two possible solutions for the intracavity power for a particular pump laser detuning. The two solutions correspond to blue and red detuned operation of the pump laser. The combined Kerr nonlinearity and thermal effects lead to a non-Lorentzian, triangular resonance shape when the pump laser is scanned with decreasing optical frequency. The resonance frequency self-locks to the pump laser when the pump laser is blue detuned (upper branch), but becomes thermally unstable when red detuned (lower branch). This self-stability is exploited in microresonator-based frequency comb generation. In this work, tuning the pump laser through the effective zero detuning frequency into the lower branch (effectively red detuned) after following the upper branch leads to the formation of temporal dissipative cavity solitons. This regime is qualitatively different from the stable operating regime of microresonator-based frequency combs, which rely on pumping from the blue sideband and do not cross the zero-detuning point. The soliton pulses form spontaneously without external stimulation. The number of solitons can be controlled by the pump laser detuning. The generated solitons remain stable until the pump laser is switched off without active feedback. This remarkable stability in the presence of solitons, despite operating on the usually thermally unstable lower branch, is discussed. The discovery enables converting a continuousTemporal dissipative solitons have been observed in a high-Q optical microresonator. These solitons are spontaneously generated when the pump laser is tuned through the effective zero detuning point of a high-Q resonance, leading to red-detuned pumping. This regime is fundamentally new in nonlinear microresonators and is stable without active feedback. The number of solitons can be controlled via pump laser detuning, and transitions between soliton states are associated with discontinuous steps in resonator transmission. The solitons correspond to low-noise optical frequency combs with smooth spectral envelopes, critical for applications in broadband spectroscopy, telecommunications, astronomy, and low phase-noise microwave generation. High-Q nonlinear optical microresonators, such as dielectric whispering gallery mode or ring-type resonators, have attracted significant attention. Frequency comb generation in these resonators has evolved into a research field. The comb lines are generated via cascaded four-wave mixing (FWM), resulting in hundreds of equidistant and coherent optical lines. The comb line spacing corresponds to the free-spectral range of the microresonator. These combs can perform at levels required for optical frequency metrology, but often suffer from significant noise and do not correspond to ultra-short pulses in the time domain. In strongly driven nonlinear microresonators, the intracavity field as a function of the pump laser detuning cannot be described by a Lorentzian shape. Instead, the resonance is asymmetrically shifted towards lower frequencies due to Kerr nonlinearity. This leads to bistable behavior, with two possible solutions for the intracavity power for a particular pump laser detuning. The two solutions correspond to blue and red detuned operation of the pump laser. The combined Kerr nonlinearity and thermal effects lead to a non-Lorentzian, triangular resonance shape when the pump laser is scanned with decreasing optical frequency. The resonance frequency self-locks to the pump laser when the pump laser is blue detuned (upper branch), but becomes thermally unstable when red detuned (lower branch). This self-stability is exploited in microresonator-based frequency comb generation. In this work, tuning the pump laser through the effective zero detuning frequency into the lower branch (effectively red detuned) after following the upper branch leads to the formation of temporal dissipative cavity solitons. This regime is qualitatively different from the stable operating regime of microresonator-based frequency combs, which rely on pumping from the blue sideband and do not cross the zero-detuning point. The soliton pulses form spontaneously without external stimulation. The number of solitons can be controlled by the pump laser detuning. The generated solitons remain stable until the pump laser is switched off without active feedback. This remarkable stability in the presence of solitons, despite operating on the usually thermally unstable lower branch, is discussed. The discovery enables converting a continuous