Superlubricity, a phenomena of vanishing friction, has been studied theoretically and experimentally. It is theoretically shown that certain unique cases exist where friction force exactly vanishes when the atomic arrangements on the contacting surfaces satisfies the condition for the appearance of superlubricity. The experiments agree with the theoretical predictions. The measurements on atomically clean surfaces show that friction forces decrease as the contacting conditions approach those for the appearance of superlubricity. Friction is not observed in the superlubricity regime in the measurements capable of resolving a friction force of 3 nN by scanning tunneling microscopy.