 By the 1980s, the Grand Prix tour was the main men's tennis tour, while WCT events were in certain years even part of the Grand Prix circuit.In 1990, all top tier tour events became part of the ATP Tour as the Association of Tennis Professionals took control of professional tour tennis from the ITF's Men's Tennis Council.Challenger tournaments were begun in 1978 and initially were separate events that did not comprise a unified tour.