3D FISH of Roberts sub-chromosomal domain territories. Views of Imaris' reconstructions of trophoblasts and fibroblasts nuclei after three-dimensional FISH with probes for PH1 (Chr1), centromeric régions of chromosome 4 (Chr4), 9 (Chr9) and 16 (Chr16). Cells were counterstained with DAPI (blue). (A) Control cells hybridized with PH1 probe (trophoblasts: red probe and a fibroblast: green probe). (B) RBS cells with split signal of one or two territories (chr 1, chr 4, chr 9 and chr 16). (C) Focus on split spots of PH1 showing the bridge between the two signals (arrows).