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The reverse process, known as mesenchymalвЂ“epithelial transition (MET), also occurs frequently during development. Moreover, EMT is known to be activated during cancer pathogenesis and tissue fibrosis. It is now widely accepted that EMT occurs normally during early embryonic development, to enable a variety of morphogenetic events, as well as later in development and during wound healing in adults. EMT, epithelialвЂ“mesenchymal transition.Д®MT was first described by researchers studying early embryogenesis as a programme with well-defined cellular features 1, 2. The accumulated loss or gain of epithelial/mesenchymal (E/M) characteristics pushes a cell towards various intermediate states (bottom left and right) in a fluid and reversible manner, between a complete epithelial (middle left) and a complete mesenchymal (middle right) state. Mesenchymal cells contain vimentin-based intermediate filaments and utilize integrin-containing focal adhesions to attach to the extracellular matrix. By contrast, mesenchymal cells do not contain functional epithelial junctions and present a backвЂ“front polarity in their actin stress fibres. Epithelial cells are attached to the underlying basement membrane via hemidesmosomes, which contain integrin to allow binding to the basement membrane and are also linked to cytokeratins inside the cell. Polarity complexes, including the Par, Crumbs and Scribble complexes, define the apical versus basolateral domains of an epithelial cell. ApicalвЂ“basal polarity guides proper organization of the tight junctions, adherens junctions and desmosomes in epithelial cells. Tight junctions are localized at the apical-lateral contact points in order to help maintain epithelial polarity. Adherens junctions are connected to cortical actin bundles, while desmosomes are linked with cytokeratin intermediate filaments. Epithelial cells are connected with each other via a variety of epithelial cell junctions, including adherens junctions, desmosomes, gap junctions and tight junctions. Various cellular features associated with an epithelial or a mesenchymal cell state are found in a range of combinations and to different degrees in cells in different developmental contexts. While recognizing the importance of maintaining diversity in experimental approaches and conceptual frameworks, we emphasize that lasting contributions of EMT research to increasing our understanding of developmental processes and combatting cancer and other diseases depend on the adoption of a unified terminology to describe EMT. We trust that these guidelines will help to reduce misunderstanding and misinterpretation of research data generated in various experimental models and to promote cross-disciplinary collaboration to identify and address key open questions in this research field. This Consensus Statement, mediated by вЂthe EMT International AssociationвЂ™ (TEMTIA), is the outcome of a 2-year-long discussion among EMT researchers and aims to both clarify the nomenclature and provide definitions and guidelines for EMT research in future publications. This growing interest warrants the need for a consensus among researchers when referring to and undertaking research on EMT. With over 5,700 publications indexed by Web of Science in 2019 alone, research on EMT is expanding rapidly. EMT occurs in a diverse range of physiological and pathological conditions and is driven by a conserved set of inducing signals, transcriptional regulators and downstream effectors. Nature Reviews Molecular Cell Biology volumeВ 21, pages 341вЂ“352 ( 2020) Cite this articleД®pithelialвЂ“mesenchymal transition (EMT) encompasses dynamic changes in cellular organization from epithelial to mesenchymal phenotypes, which leads to functional changes in cell migration and invasion. On behalf of the EMT International Association (TEMTIA).Guidelines and definitions for research on epithelialвЂ“mesenchymal transition

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