Oct4 and Sox2 transcription factors (belonging to the Yamanaka's factor family) and Nanog, named together as core transcription factors of pluripotency, are indispensable to induce and maintain the pluripotency state. They act generally as activators of genes coding for transcription factors, cofactors and chromatin regulators. They also activate microRNA expression. In addition, Oct4, Sox2 and Nanog function as repressors of genes for factors responsible for escape from pluripotency and differentiation. Core transcription factors positively regulate their own promoters, forming a positive-feedback loop. In recent times, researchers' attention has been attracted towards Oct4, Sox2 and Nanog as potential markers for cancer stem cells (CSCs). The expression of these factors has been confirmed in numerous types of tumors. The aim of this paper is to concisely review features of core transcription factors and their role in embryogenesis and tumorigenesis including the CSC hypothesis.