In response to various stimuli, neutrophils may release extracellular network (NET – neutrophil extracellular trap) consisting of DNA, proteolytic enzymes and other components of the cell nucleus. The NETosis process was first described in 2004 by Brinkmann et al. as animmunological response to Gram-positive bacteria, Gram-negative bacteria. Other sources provide data referring to the created network in response to the activity of fungi, protozoa and viruses. It is a mechanism of programmed cell death that leads to chromatin decondensation in the nucleus, disintegration of cell organelles and mixing of their constituent, as well as cell membrane permeabilization. The ability to release similar networks is also demonstrated by mast cells (MCET – mast cell extracellular trap), eosinophils (EET – eosinophil extracellular trap) and macrophages (MET – macrophage extracellular trap). Various microscopy techniques, for example, immunofluorescence microscopy, transmission electron microscopy, and scanning electron microscopy, flow cytometry and ELISA tests are used to better illustrate and evaluate the NETosis markers. Current knowledge regarding the formation of NETs suggests in-vitro qualitative microscopic examination. So far, measurements based on flow cytometry allow for quick and objective evaluation of several thousand cells simultaneously. The application of cytometry facilitates indirect detection of NET producing cells in blood samples. While ELISA technique, due to the simplicity of making measurements and wide availability of validated tests, may contribute to its routine usage as a tool in screening tests.