The dynamic contribution of domain walls (DWs) to application‐relevant dielectric and piezoelectric properties of ferroelectrics and relaxor‐based oxide ceramics has been in the focus since the earliest studies on these complex multifunctional materials. Despite the vital importance of DWs in the material design for targeted applications, the understanding of these interfaces has been significantly advanced only recently owing to the concurrent development of analytical methodologies probing the structure of samples in situ and at different length scales. In this contribution, we present two recent cases that have raised particular attention and controversy. The first is on the electrically conductive DWs in BiFeO3 (BFO), whereas the second is on low‐angle DWs characteristic for relaxor ferroelectric Pb(Mg1/3Nb2/3)O3−xPbTiO3 (PMN–PT). Using nonlinear piezoelectric measurements with the support from multiscale structural analysis, we illustrate with the two case studies how, on one hand, the local electrical conductivity in BFO and, on the other hand, the structural disorder inherent to PMN–PT affect DW dynamics, leading to emerging macroscopic effects. By clarifying some of the aspects of these particular interfaces, we hope that the presented results will provide guidance to analytical approaches for identifying the key microscopic mechanisms contributing to macroscopic functional properties of ferroelectric and related materials.