A Hall thruster is powering many of the satellites moving around Earth right now. It needs 100 million (yes, you read that right, 100 million) times less fuel than chemical thrusters. But it was never remotely sturdy enough to get anything to Mars—until now.
Today, we use ion thrusters to correct satellite orbits and visit asteroids. In 100 years, we might be using them to propel massive generation ships that send colonists to a different part of the galaxy.