Abstract: For decades, it was believed that direct evidence of extra spatial dimensions would always be far beyond the reach of accelerators. Recent developments indicate that this may not be the case. There are strong motivations for believing that extra dimensions might be detected in the next generation of colliders. I review these developments, and then turn to a specific model of "universal extra dimensions". In this model, some of the Kaluza-Klein quarks will be very long-lived, and can thus hadronize and form bound states. The signatures of these states at a linear collider are spectacular and virtually background-free.