Complex oxides system displays exotic properties such as high temperature superconductivity, colossal magnetoresistance and multiferroics. Owing to the strong correlation between lattice, spin, charge and orbital degrees of freedom, competing electronic states in complex oxides system often have close energy scales leading to rich phase diagrams and spatial coexistence of different electronic phases known as electronic phase separation (EPS). When the dimension of complex oxides system is reduced to the length scale of the correlation length of the EPS, one would expect fundamental changes of the correlated behavior. This offers a way to control the physical properties in the EPS system. In this paper, we review our recent works on electronic phase separation in complex oxide systems. We discovered a pronounced ferromagnetic edge state in manganite strips; by using lithographic techniques, we also fabricated antidot arrays in manganite, which show strongly enhanced metal-insulator transition temperature and reduced resistance. Moreover, we discovered a spatial confinement-induced transition from an EPS state featuring coexistence of ferromagnetic metallic and charge order insulating phases to a single ferromagnetic metallic state in manganite. In addition, by using unit cell by unit cell superlattice growth technique, we determined the role of chemical ordering of the dopant in manganite. We show that spatial distribution of the chemical dopants has strong influence on their EPS and physical properties. These works open a new way to manipulate EPS and thus the global physical properties of the complex oxides systems, which is potentially useful for oxides electronic and spintronic device applications.