It was 24 January 1986 when Voyager 2 flew by Uranus on its never-ending outbound journey from the solar system. Three and a half years later, on 25 August 1989, the probe flew past Neptune and became the only spacecraft to ever visit Uranus and Neptune.
After those flybys, the ice giants passed from space agencies’ immediate plans in favor of missions to Mars, Jupiter, Saturn, and Mercury that would largely help human exploration into the solar system.