Cold Spring Harbor Laboratory (CSHL) Fellow Jason Sheltzer and his lab study the abnormal segregation of chromosomes that occurs in cancer. In a study published in Developmental Cell, they tracked chromosome movements during cell division. In this video, the chromosomes are stained green; they double and split between two new cells. Normally, cells have phases and checkpoints that ensure chromosomes are organized and lined up correctly for equal distribution. But when the researchers disrupted that checkpoint system, some chromosomes ended up on the wrong side. Sheltzer and his laboratory discovered that this unequal division of chromosomes helps some cancers become resistant to therapeutic drugs. These videos were taken by the first author of the study, Devon Lukow, a Stony Brook University graduate student-in-residence in the Sheltzer lab, using a confocal microscope.