The article provides an overview of epithelial-mesenchymal transition (EMT), a process where polarized epithelial cells undergo biochemical changes to acquire a mesenchymal phenotype, characterized by enhanced migratory capacity, invasiveness, and ECM component production. EMT is initiated by various molecular processes, including transcription factor activation, cell-surface protein expression, cytoskeletal reorganization, and ECM-degrading enzyme production. The authors classify EMT into three distinct biological subtypes: type 1 EMT, which occurs during implantation, embryogenesis, and organ development; type 2 EMT, associated with tissue regeneration and fibrosis; and type 3 EMT, linked to cancer progression and metastasis. Each subtype has distinct functional consequences and is driven by different signaling pathways. Type 1 EMT is reversible and essential for embryonic development, while type 2 EMT is associated with chronic inflammation and fibrosis. Type 3 EMT is crucial for cancer invasion and metastasis, facilitated by genomic alterations in cancer cells. The article highlights the importance of EMT in various biological contexts and suggests that future research will focus on understanding the molecular mechanisms and signaling pathways involved in each subtype of EMT.The article provides an overview of epithelial-mesenchymal transition (EMT), a process where polarized epithelial cells undergo biochemical changes to acquire a mesenchymal phenotype, characterized by enhanced migratory capacity, invasiveness, and ECM component production. EMT is initiated by various molecular processes, including transcription factor activation, cell-surface protein expression, cytoskeletal reorganization, and ECM-degrading enzyme production. The authors classify EMT into three distinct biological subtypes: type 1 EMT, which occurs during implantation, embryogenesis, and organ development; type 2 EMT, associated with tissue regeneration and fibrosis; and type 3 EMT, linked to cancer progression and metastasis. Each subtype has distinct functional consequences and is driven by different signaling pathways. Type 1 EMT is reversible and essential for embryonic development, while type 2 EMT is associated with chronic inflammation and fibrosis. Type 3 EMT is crucial for cancer invasion and metastasis, facilitated by genomic alterations in cancer cells. The article highlights the importance of EMT in various biological contexts and suggests that future research will focus on understanding the molecular mechanisms and signaling pathways involved in each subtype of EMT.