Micro-mixing is an important mechanism

which works simultaneously with macro-mixing in chemical reactors in process industries

for achieving the best selectivity with respect to desired products.In about a half century

a huge amount of data and knowledge has been accumulated from theoretical and experimental studies on micromixing.Nevertheless

those results are mostly composites of simplified theoretical and empirical models

and the true nature of interactions of flow inhomogeneity and micro-mixing with chemical reaction has not been fully unveiled.This article reviews the progress in micro-mixing study in chemical reactors to date.A few important topics related to the nature

experimental evaluation

and numerical simulation of micro-mixing are addressed.Some suggestions are given hopefully to motivate more chemical engineers to devote their efforts to better understanding of micro-mixing in chemical reactors.