Intrinsic polar materials, such as metal-oxides and compound semiconductors, are some of the most commonly used materials in electronic, magnetic, and chemical applications.It has been recognized for some time that polarity arising from chemical variations at surfaces and interfaces is the main driving force determining the structural and electronic properties of nanoscale materials. In this talk I will discuss the possible mechanism of polar oxide film growth on case of MgO(111), as well as atomic and electronic structure of polar oxide/oxide and polar oxide/semiconductor interfaces. Also I will give examples how the interface polarity can be effectively use for stabilisation of metastable thin film phases such as cub-GaN(111)/MgO(111), and large band offsets engineering at polar oxide/semiconductor interfaces.