Stem cells are marked in individual colors by the multicolor Cre reporter Confetti. (a) Each crypt becomes monochromatic over time (bottom of image), producing parallel bands of differently colored cells on villus flanks. (b) Confocal sectioning through multiple crypt bottoms. When individual stem cells are marked with different Confetti colors, crypts resolve to monoclonality (that is, they become monochromatic in 4 to 8 weeks due to neutral competition of the stem cells). All images in this figure were reproduced with permission from Elsevier, from Snippert H et al.: Cell 2010, 143:134-144.