The article reviews the role of epithelial-mesenchymal transition (EMT) in tumor metastasis. EMT is a critical process where epithelial cells lose their adherens junctions, gain motility, and invade surrounding tissues, which is essential for cancer progression and metastasis. The review highlights key evidence from studies using human cancer cell lines, mouse models, and clinical human cancer tissues. It discusses the molecular regulators of EMT, such as transcription factors (SNAIL, TWIST, ZEB), and signaling pathways (TGF-β, WNT, NOTCH). The article also explores the challenges and controversies in understanding EMT in metastasis, including the reversible nature of EMT and the difficulty in detecting transient EMT states in human tumor samples. Finally, it examines the therapeutic implications of targeting EMT in metastatic cancer, emphasizing the need for careful consideration of EMT's dynamic cellular plasticity.The article reviews the role of epithelial-mesenchymal transition (EMT) in tumor metastasis. EMT is a critical process where epithelial cells lose their adherens junctions, gain motility, and invade surrounding tissues, which is essential for cancer progression and metastasis. The review highlights key evidence from studies using human cancer cell lines, mouse models, and clinical human cancer tissues. It discusses the molecular regulators of EMT, such as transcription factors (SNAIL, TWIST, ZEB), and signaling pathways (TGF-β, WNT, NOTCH). The article also explores the challenges and controversies in understanding EMT in metastasis, including the reversible nature of EMT and the difficulty in detecting transient EMT states in human tumor samples. Finally, it examines the therapeutic implications of targeting EMT in metastatic cancer, emphasizing the need for careful consideration of EMT's dynamic cellular plasticity.