By allowing easy labeling of chromosomal and nuclear proteins and the tagging of specific chromosomal regions,the use of green-fluorescent protein (GFP) has provided new and special opportunities for directly observing chromosome dynamics in vivo. Here, we review recent applications of this methodology, focusing particularly on examples where new biology has been learned, or at least sighted. In particular, we focus on active bacterial chromosome segregation, yeast mitosis and centromere dynamics, and large-scale chromatin structure and dynamics within eukaryotic interphase nuclei.