Frequency modulation atomic force microscopy (FM-AFM) has been a powerful tool for imaging atomic-scale structures and properties of various materials including metals, semiconductors, metal oxides, alkali halides and organic systems. Whilst the method has been used mainly in ultrahigh vacuum environments, recent progress in FM-AFM instrumentation made it possible to apply this technique also to investigations in liquid. This technological innovation opened up a variety of applications of FM-AFM in biology and electrochemistry. To date, the improved FM-AFM instrument and technique have been applied to investigations of several biological materials, providing novel information that has not been accessible with other imaging techniques. In this review, I will summarize the recent progress in FM-AFM instrumentation and biological applications in liquid.