Oxide films with a thickness of just a few atoms can now be grown with a precision matching that of semiconductors. This opens up a whole world of functional device concepts and fascinating phenomena that would not occur in the expanded bulk crystal. Particularly interesting phenomena occur in films showing magnetic or electric order or, even better, both of these (“multiferroics”). Here, I will focus on epitaxy. After a brief introduction to the concept of the epitaxial deposition, I will discuss the growth modes and growth processes involved. The major deposition techniques will be described as well as the main characterization tools to assess the epitaxial nature of oxide thin films. Because of the strong lattice polarization coupling in ferroelectrics, epitaxy is a great tool to engineer polarization in thin films. Epitaxial strain, chemical control on interface atomic termination and charge screening environment tuning are key elements of the ferroelectric domain design. In the ultrathin regime however, the dominating effect of the depolarizing field leads to a suppression of the thin film functionality, i. e. the ferroelectric polarization. Here, I will present such effect and the physics of ultrathin regime and discuss routes towards robust polarization states in the ultrathin form. Furthermore, because most ferroelectric materials are deposited in their ferroelectric phase, in-situ monitoring of polarization is possible. I will present the state of the art dealing with such a capacity and demonstrate how in-situ tracking of ferroelectricity can advance the integration of such functional materials into nanoscale devices.