The concept of flow "fine" synthesis,that is high yielding and selective organic synthesis by flow methods,will be presented.Flow methods have several advantages over batch methods in terms of environmental compatibility,efficiency,and safety.However,synthesis by flow methods is more difficult than synthesis by batch methods.Indeed,it has been considered that synthesis by flow methods can be applicable for the production of simple gasses but that it is difficult to apply to the synthesis of complex molecules such as natural products and active pharmaceutical ingredients(APIs).Therefore,organic synthesis of such complex molecules has been conducted by batch methods.On the other hand,syntheses and reactions that attain high yields and high selectivities by flow methods are increasingly reported.Flow methods are leading candidates for the next generation of manufacturing methods that can mitigate environmental concerns toward sustainable society.