Can you recognize someone you haven't seen in years, but forget what you had for breakfast yesterday? Our brains constantly rearrange their circuitry to remember familiar faces or learn new skills, but the molecular basis of this process isn't well understood. Today, scientists report that sulfate groups on complex sugar molecules called glycosaminoglycans (GAGs) affect "plasticity" in the brains of mice. Determining how GAGs function could help us understand how memory and learning work in humans, and provide ways to repair neural connectivity after injuries.