The study of small magnetic features and nanostructures has attracted much attention due to interest in both technological applications and fundamental research in micromagnetism. For their characterization, a visualization technique with high lateral resolution is required. Among the wealth of techniques, magnetic force microscopy (MFM) has become a powerful tool for visualizing submicronsized domain structures. This is mainly due to its ease of use without any specific sample preparation and the high lateral resolution of a few 10 nm. MFM is a sensitive and useful technique for direct observation of magnetic domains and their magnetic behavior, which can help elucidate properties of magnetic films and nanostructures. This chapter reviews MFM techniques and applications that demonstrate the achievement of MFM in magnetic materials and nanoscience research. The review focuses on the current MFM study involved with magnetic features and nanostructures, including magnetic interactions in nanostructured thin films and nanomagnetic patterns with special emphasis on the recent research in micromagnetism acquiring from our SPM laboratory.