Ferromagnetic thin films have been investigated in the last few decades for the advancement of the fundamental research and data storage technology. It is necessary to understand the magnetic properties like domain structure and magnetization reversal of magnetic thin films. Formation of domains depends on energy minimization of exchange energy, magnetostatic energy, and anisotropy energy. Various types of domain walls exist such as 90°, 180° and 360° etc. In my lecture I will show how the change in anisotropy, interactions, and interface in ferromagnetic films can lead to various types of domains and domain walls. The magnetization reversal can be studied simultaneously with domain imaging using the state-of-art magneto-optic Kerr effect (MOKE) microscopy. The domain structure has been studied in Co films deposited on Si (100) and MgO (100) substrates exhibiting uniaxial and mixture of uniaxial and cubic anisotropies. Shape anisotropy effect has been studied in magnetic antidot lattice which are periodic array of holes embedded in ferromagnetic thin films. We will discuss how the inter-layer interactions can lead to layer-by-layer magnetization reversal in ferromagnetic/non-magnetic multilayers. In contrary in magnetic dot arrays the dipolar interaction leads to superferromagnetic domain state. Further we will discuss how magnetic interface can be engineered at the interface between magnetic and non-magnetic (organic) thin films. In this regard I will review our recent results on creating magnetic fullerene (interface) in Fe/C60 bilayers. It has been found that the magnetic fullerene can exhibit magnetic moment of ~ 3 µB per cage. I will also discuss how the interface between two magnetic layers can be engineered to exhibit tunable damping properties.