An in vitro method of detecting the presence of or confirming the absence of residual pluripotent stem cells in a population of cells differentiated from said pluripotent stem cells, comprising: (a) providing a population of differentiated cells under conditions that favor growth or maintenance of said pluripotent stem cells; (b) applying a first stain and a second stain to said cell population, wherein said first stain detects a first marker the expression of which is indicative of the presence of said pluripotent stem cells; and said second stain detects a second marker the expression of which is indicative of the presence of said pluripotent stem cells, and (i) wherein said first stain is detectable under visible light and said second stain is detectable under ultraviolet light, or (ii) wherein said first stain is detectable under visible light and said second stain is detectable under visible light, and wherein said first stain and said second stain are visually distinguishable; or (iii) wherein said first stain is observable under visible light and under ultraviolet light and said second stain is detectable under ultraviolet light, or (iv) wherein said first stain is observable under visible light and under ultraviolet light and said second stain is detectable under visible light; (c) microscopically observing cells of said cell population under visible or ultraviolet light to detect any cells that are positive for said first marker; (d) microscopically observing cells that are positive for said first marker under visible or ultraviolet light and determining whether any of said cells are positive for said first marker and said second marker; and (e) identifying a cell that is positive for said first marker and said second marker as a pluripotent stem cell, or confirming the absence of pluripotent stem cells if no cell positive for said first marker and said second marker is identified. (a) providing a population of differentiated cells under conditions that favor growth or maintenance of said pluripotent stem cells; (b) applying a first stain and a second stain to said cell population, wherein said first stain detects a first marker the expression of which is indicative of the presence of said pluripotent stem cells; and said second stain detects a second marker the expression of which is indicative of the presence of said pluripotent stem cells, and (i) wherein said first stain is detectable under visible light and said second stain is detectable under ultraviolet light, or (ii) wherein said first stain is detectable under visible light and said second stain is detectable under visible light, and wherein said first stain and said second stain are visually distinguishable; or (iii) wherein said first stain is observable under visible light and under ultraviolet light and said second stain is detectable under ultraviolet light, or (iv) wherein said first stain is observable under visible light and under ultraviolet light and said second stain is detectable under visible light; (i) wherein said first stain is detectable under visible light and said second stain is detectable under ultraviolet light, or (ii) wherein said first stain is detectable under visible light and said second stain is detectable under visible light, and wherein said first stain and said second stain are visually distinguishable; or (iii) wherein said first stain is observable under visible light and under ultraviolet light and said second stain is detectable under ultraviolet light, or (iv) wherein said first stain is observable under visible light and under ultraviolet light and said second stain is detectable under visible light; (c) microscopically observing cells of said cell population under visible or ultraviolet light to detect any cells that are positive for said first marker; (d) microscopically observing cells that are positive for said first marker under visible or ultraviolet light and determining whether any of said cells are positive for said first marker and said second marker; and (e) identifying a cell that is positive for said first marker and said second marker as a pluripotent stem cell, or confirming the absence of pluripotent stem cells if no cell positive for said first marker and said second marker is identified.