The article reviews the recent advancements in the understanding of domain walls in ferroelectric and multiferroic materials, highlighting their complexity and unique properties. It begins by discussing the formation of domains and domain walls, emphasizing the role of boundary conditions and the energy minimization principles. The review then delves into the scaling laws that govern domain sizes, particularly Kittel's law, which predicts a square root dependence of domain width on film thickness. This law is extended to nonplanar structures and superlattices, considering the effects of surface interactions and critical thicknesses. The article also explores more complex domain morphologies, such as vertices, vortices, and quadrupoles, which arise in extreme confinement or when multiple order parameters are coupled. These topological defects, including ferroelectric vortices, are discussed in detail, along with their potential applications in memory devices. The functional properties of these defects, such as conductivity, are also examined. Finally, the review discusses nanodomains in bulk materials, particularly in relaxors, where nanoscopic polar domains can significantly influence the material's electromechanical properties. The presence of a large concentration of domain walls in these materials suggests that they may contribute to their exceptional behavior, such as colossal magnetoresistance and superelasticity.The article reviews the recent advancements in the understanding of domain walls in ferroelectric and multiferroic materials, highlighting their complexity and unique properties. It begins by discussing the formation of domains and domain walls, emphasizing the role of boundary conditions and the energy minimization principles. The review then delves into the scaling laws that govern domain sizes, particularly Kittel's law, which predicts a square root dependence of domain width on film thickness. This law is extended to nonplanar structures and superlattices, considering the effects of surface interactions and critical thicknesses. The article also explores more complex domain morphologies, such as vertices, vortices, and quadrupoles, which arise in extreme confinement or when multiple order parameters are coupled. These topological defects, including ferroelectric vortices, are discussed in detail, along with their potential applications in memory devices. The functional properties of these defects, such as conductivity, are also examined. Finally, the review discusses nanodomains in bulk materials, particularly in relaxors, where nanoscopic polar domains can significantly influence the material's electromechanical properties. The presence of a large concentration of domain walls in these materials suggests that they may contribute to their exceptional behavior, such as colossal magnetoresistance and superelasticity.