The images show the microtubule-based spindle fibers (red), chromosomes (blue), and their kinetochores (green). Microtubules align chromosomes in the middle of the spindle in the presence of the newly discovered protein called BuGZ (+BuGZ), but mis-aligned in its absence (-BuGZ). Chromosome misalignment leads to its mis-segregation during cell division. Scale bar, 5 microns. Courtesy of Yixian Zheng.