Embryonic stem cells are derived from the inner cell mass of the blastocyst, the early stage of an embryo that is formed 5-6 days after fertilization. They are pluripotent, meaning they are able to differentiate into multiple cell types, and they are also capable of unlimited self-renewal. These properties of embryonic stem cells make them valuable tools for studying normal development, modeling disease, and developing cell-based regenerative therapies. Identifying and characterizing embryonic stem cells involves detecting cellular markers with techniques such as flow cytometry, immunocytochemistry (ICC), immunohistochemistry (IHC), and enzyme-linked immunosorbent assay (ELISA). The types of markers most commonly used include transcription factors, cell surface proteins, and a broad range of intracellular signaling molecules. In most cases, a combination of several markers must be detected on the same cell to enable its definitive identification. Transcription factors serving as embryonic stem cell markers include Nanog, Oct4, and Sox2, all of which have a central role in maintaining pluripotency. Examples of cell surface proteins that are similarly exploited include the cluster of differentiation antigens CD9, CD29, and CD133; the stage specific embryonic antigens SSEA-3 and SSEA-4; and the TRA-1-60 and TRA-1-81 proteins. Intracellular signaling molecules which function as embryonic stem cell markers include members of the LIF/STAT3, BMP/SMAD, and Wnt/β-catenin signaling pathways. The overlap in marker expression between different cell types represents a major challenge for stem cell research. Notably, many embryonic stem cell markers are also expressed by tumor stem cells, including CD133 (pancreatic cancer stem cells), SSEA-3 (breast cancer stem cells), and TRA-1-60 (germ cell tumors of the testis). Matters are further complicated by the fact that human and mouse stem cells vary in the mechanisms used to regulate pluripotency and differentiation. For these reasons, high quality research reagents are essential to fully leverage the benefits that embryonic stem cells have to offer. We offer a wide range of embryonic stem cell markers including EpCAM antibodies, OCT4 antibodies, SOX2 antibodies, CD9 antibodies, and CD133 antibodies, covering various host species, isotypes, and conjugates. Our antibodies are validated for use in multiple applications and come with recommended protocols which can provide a starting point for optimizing your own model system. Because many of our antibodies are literature cited and reviewed by our customers, as well as backed by expert technical support, you can have confidence in your results.