The image shows a defective ribosome as observed in congenital ribosomopathies and in cancer. Presence of such a defective ribosome causes high levels of reactive oxygen species (ROS) in cells, as illustrated by the bubbles surrounding the ribosome. In this issue, Sulima and colleagues show that these elevated ROS levels play an essential role in the paradoxical transition from hypo- to hyperproliferation phenotypes in the presence of ribosome defects. For details, see article by Sulima and colleagues on page 320.