Recent developments in ferroelectric (FE) domain imaging techniques have established an understanding of intriguing polarization switching dynamics. In particular, nanoscale studies of FE domain switching phenomena using piezoresponse force microscopy (PFM) can provide important microscopic details on nucleation and subsequent growth of domains, complementing conventional electrical measurements that only give macroscopic information. This review covers recent nanoscale PFM studies of domain switching dynamics in FE thin films. Recent nanoscale PFM-based studies have demonstrated that quenched defects inside the FE thin films play important roles in domain switching processes, including defect-mediated inhomogeneous nucleation, pinning-dominated nonlinear dynamics of domain walls, and many other intriguing phenomena. (C) 2011 Elsevier B.V. All rights reserved.