Protein expression is a technique in which proteins are synthesized, modified and regulated in living organism. Protein expression is used to study for the presence of one or more proteins in the cell or tissue. Protein expression is used by pharmaceutical companies, biotechnology companies, academic research institutes, contract research organizations and others for proteomics. On the basis of expression systems, protein expression market can be segmented into insect cell expression systems, prokaryotic expression systems, mammalian cell expression systems, yeast expression systems and other expression systems. On the basis of application, protein expression market can be segmented into industrial proteins, therapeutic proteins and research applications. On the basis of products, protein expression market can be classified into expression vectors, reagents, competent cells, instruments and services. Protein expression is used in manufacturing of commercial proteins which are used in pharmaceutical and biotechnology companies.