This review presents an application of micromixer technologies, which have driven a number of critical research trends over the past few decades, particularly for chemical and biological fields. Micromixer technologies in this review are categorized according to their applications: (1) chemical applications, including chemical synthesis, polymerization, and extraction; (2) biological applications, including DNA analysis, biological screening enzyme assays, protein folding; and (3) detection/analysis of chemical or biochemical content combined with NMR, FTIR, or Raman spectroscopies. In the chemical application, crystallization, extraction, polymerization, and organic synthesis have been reported, not only for laboratory studies, but also for industrial applications. Microscale techniques are used in chemical synthesis to develop microreactors. In clinical medicine and biological studies, microfluidic systems have been widely applied to the identification of biochemical products, diagnosis, drug discovery, and investigation of disease symptoms. The biological and biochemical applications also include enzyme assays, biological screening assays, cell lysis, protein folding, and biological analytical assays. Nondestructive analytical/detection methods have yielded a number of benefits to chemical and biochemical processes. In this chapter, we introduce analytical methods those are frequently integrated into micromixing technologies, such as NMR, FT-IR, and Raman spectroscopies. From the study of micromixers, we discovered that the Re number and mixing time depends on the specific application, and we clustered micromixers in various applications according to the Re number and mixing performance (mixing time). We expect that this clustering will be helpful in designing of micromixers for specific applications.