关键词: 光学显微镜；衍射极限；超分辨；超级透镜；超振荡

Abstract: By considering the smallest feature that can be observed by an optical microscope, the development of optical microscopy and the efforts made to break the diffraction limit were reviewed. Optical microscopy is crucial for science at small scales. Although the diffraction limit has been overcome, the continuous effort made in this field would enable a further improvement in resolution.

Key words: optical microscopy; diffraction limit; super resolution; superlens; superoscillation