Transition metal oxides (TMOs) display a large variety of novel magnetic and electronic properties due to the strong interplay between spin, charge, lattice, and orbital degrees of freedom. By epitaxially growing TMOs on appropriate substrates, the complex oxide heterostructures can behave very differently from their bulk counterparts, largely due to the epitaxial strain, interfacial coupling, and/or interfacial electronic reconstruction. In this talk, we will present our recent works on two types of oxide heterostructures, i.e, ferromagnetic SrRuO3 / La0.67Sr0.33MnO3 bilayers and tensile-strained EuTiO3. For the bilayer system, we will discuss the formation of unusual spin structures within the SrRuO3 layer resulting from the competition of antiferromagnetic interfacial coupling and Zeeman interaction, which in turn determines the magnetization reversal of the La0.67Sr0.33MnO3 layer and the magnetotransport behavior. We will then show a strain-enabled multiferroic (ferromagnetic and ferroelectric) material EuTiO3, which is a paraelectric antiferromagnet in its bulk form, and the structural control of its magnetic anisotropy.