"Phase-field modeling of ferroelectric phase transitions, domain evolution, and switching in thin films" - This seminar will discuss the applications of the phase-field approach to predicting phase transitions, domain structures, and properties of ferroelectric thin films. In this approach, a nanoscale domain structure is described using a set of spatially inhomogeneous distributions of order parameters such as polarization and strains. Their temporal evolution toward equilibrium is obtained by solving the coupled time-dependent Ginzburg-Landau equations as well as the electrostatic and mechanical equilibrium equations. In particular, it will be shown that one can use it to not only help interpreting experimental observations but also provide guidance to achieve desirable transition temperatures, specific domain states, domain wall orientations, and domain wall mobility. It will also be shown that mechanical boundary conditions and stress distributions may be manipulated to tune the coercive field and dramatically enhance piezoelectric responses of ferroelectric thin films. Examples to be discussed are drawn from recent collaborations between the author's group in continuum and mesoscale modeling and a number of experimental groups on oxide film growth and characterizations.