Non-invasive multiple reporter visualization in ES cells. (a-d) a mixture of CK6/ECFP (ECFP+) and YC5/EYFP (EYFP+) ES cells at low density. (a) image taken under bright field with no epifluorescence. (b) dark field image taken through an EYFP filter. (c) dark field image taken through an ECFP filter. (d) dark field double exposure image acquired by consecutively using ECFP and EYFP filters. ECFP+ cells can clearly be discerned from EYFP+ cells. (e-f) culture of mixed populations of ES cells comprising ECFP+, EYFP+ and RFP+ cells. Scale bars represent 100 μm.