Walther Flemming referred to chromatin as the darkly staining (from Greek 'Khroma' for "color") nuclear material. Chromatin is DNA "packaged" with histones and other proteins. Inactive heterochromatic foci stain darkly by EM (left).
I am interested in the influence of chromatin and gene expression on stem and tumor cell biology. One important observation from our research, as one can see in the animated model above, is that the loss of Myc appears to result in dramatic spreading of heterochromatic foci. The mechanisms underlying this global chromatin function of Myc remain to be defined, but our initial evidence would suggest a dual model in which Myc operates both directly through its own DNA binding and recruitment of histone modifying enzymes but also indirectly through regulating expression of the HAT GCN5.