In the last few decades, nanoscience and nanotechnology have been growing with breath taking speed, and how to break through the diffraction limit and tame the light on a nanoscale have become the major challenges in optics. In this field, several super-resolution optical nanoscopy techniques have been developed, leading to a series of breakthroughs in physics, chemistry, and life sciences. In the work, we give a retrospect of the newly developed techniques in diffraction theory of linear optical systems, including the solid immersion lens, structured light illumination microscopy, scanning near-field optical microscopy, metamaterial-based wide field near-field imaging technique and super-oscillatory lens. Brief discussion on their principles, advantages and applications is also provided.