BACKGROUND: Extracellular trap formation (ETosis) by various blood cells has been reported. This trap contains DNA, histones and granular proteins which can elicit an innate immune response by entrapping microorganisms. The trap thus formed has been reported to have an involvement in various pathogenic conditions as well. This review focusses on the trap formation by different blood cells, the immune response associated with trap formation and also its role in various clinical conditions.METHOD: An extensive literature survey on ETosis by blood cells from 2003 to 2019 has been done. After going through the literature throughly, in this review we focuses on the trap formation by different blood cell types such as neutrophils, macrophages, eosinophils, basophils, mast cells, plasmacytoid dentritic cells, and monocytes. The mechanism with which it releases trap, the immune response it elicits and ultimately its involvement in various pathogenic conditions are described here. This article extensively covered all the above aspects and finally comprehends in nutshell the various stimuli that are currently known in trigerring the ETosis, its effect and ultimately its role in disease process. RESULTS: A clarity about the extracellular trap formation by various blood cells, mechanism of ETosis, role of Etosis in microbial invasion and in various pathogenic situations by various blood cells have been described here. CONCLUSION The current understanding about the process of ETosis and its effects has been extensively described here. Along with lot of favourable outcomes, the process of ETosis will lead to lot of pathogenic situations including thrombosis, tumour metastasis and sepsis. Current understanding about ETosis is limited. Indepth understanding of ETosis may have great therapeutic potential in the diagnosis, guiding of therapy and prognostication in various pathogenic situations including infectious conditions, autoimmune disorders and tumors.