Recent advances in ultrahigh Q Kerr-active microresonators have provided a promising platform for study of cavity nonlinear dynamics and offered a reliable route towards the vision of chip-scale ultrashort pulses and frequency combs. Optical frequency combs, with the precisely controlled spectral lines spanning over a broad spectrum, have made great impacts on precision metrology, optical clockwork, molecular fingerprinting, and many more. Chip-scale optical frequency comb will expand the already remarkable application space and become instrumental in areas where compact footprint, low power consumption, large comb spacing, and access to unconventional spectral region are essential. In this talk, I will present my recent work on these so-called Kerr frequency combs. I will first show the spontaneous pattern and dissipative soliton formation in Si3N4 ultrahigh Q microresonators. I will illustrate, via numerical modeling and analytic theory, the connection between the cavity parameters and the nonlinear evolution dynamics. Then I will describe the strategies to fully stabilize Kerr frequency combs and achieve chip-scale precision metrology. Finally, I will introduce new nonlinear phenomena which can broaden the scope of Kerr frequency comb.