Fig. 2. State of the art in FISH. (A) Many transcription sites (10) detected using barcoded probes can determine the gene expression pattern of each cell (Levsky et al., 2002) (B-D). Detection of single mRNA molecules using double or triple colored probes (Femino et al., 1998). (E) Detection of 24 chromosomes using spectral imaging (Macville et al., 1997).