Cancer stem cells (CSCs) have an increased capacity to activate antiapoptotic/prosurvival pathways as well as overexpressing ATP-binding cassette transporters which act as potent efflux pumps for potential chemotherapeutics. Aldehyde dehydrogenases (ALDH), in particular the ALDH1A1 isoform, is believed to be a reliable marker of CSCs across many cancer types, including prostate, lung, breast, esophageal, and ovarian cancers. ALDH1A1 is associated with increased chemotherapy resistance and poor clinical outcome and is an established stem cell marker.Current methods to identify ALDH in living cells are limited by cross-reactivity with several ALDH isoforms producing difficulties in data analysis and prognosis. Chan, et al. have created a ALDH1A1 isoform specific live cell dye termed Green-AlDeSense which labels cancer stem cells and exhibits a 20-fold fluorescent enhancement when bound to ALDH1A1. The dye identifies ALDH1A1 positive CSCs using live cell imaging, flow cytometry and in vivo studies.Spectral Properties: absmax: 496 nm, emmax: 516 nm.