Cover picture: Two isolated human nuclei from the brain of a normal individual, each showing trisomic aneuploidy for chromosome 21 (chr21). The three chromosome copies are painted with wholechromosome paint (green) specific for the whole q arm of chr21 and a point probe (red) specific for chr21q22.13-q22.2 using fluorescence in situ hybridization. For details, see the article by Rehen et al. in this issue (pages 2176–2180.