This book examines domain structuring due to the loss of initial phase stability in materials of finite size. It also covers aspects such as the behaviour of domain boundaries during their interaction with lattice defects, their structure in real ferroelectrically ordered materials, the effect of the lattice potential relief on their movement, and the flexural and translational components of their dynamics in ferroelectric crystals. The contribution of the domain boundaries to the dielectric properties of ferroelectrics and elastic properties of ferroelectric elastomers is evaluated