Jan Karlseder studies the role of telomeres throughout a cell’s life cycle—from the time the cell starts copying its genetic material to the time it divides into two new cells. While other researchers rely on static snapshots of telomeres’ placement and characteristics throughout this cycle, Karlseder used time-lapsed, live-cell microscopy to follow telomeres for up to 20 hours at a time. The new details have allowed him to get a fuller understanding of how telomeres move and change, how they shorten over time in normal cells, and how telomere dynamics affect the aging process and prevent cancer development.He has also spearheaded studies showing that cancer cells are able to keep their telomeres from eroding, even after many cell divisions, by using two pathways to constantly extend the telomeres. Experiments focusing on the genetics and cell biology of tumors have led Karlseder to reveal how genetic mutations in cancer cells lead to longer telomeres. One class of existing cancer drugs, Karlseder’s lab discovered, works by blocking the protective function of telomeres. Additional studies on how this works may allow Karlseder’s lab to reveal new ways of weakening or killing cancer cells by deprotecting their telomeres.