Although their first major confrontation occurred when the Mets swept the Braves in the 1969 NLCS, en route to their first World Series championship, the first playoff series won by an expansion team (also the first playoff appearance by an expansion team), the rivalry did not become especially heated until the 1990s, when a division realignment in 1994 put the Mets and the Braves in the NL East together (from 1969 to 1993, the Braves were in the NL West). The two teams faced each other again in the 1999 NLCS, and the Braves won the series four games to two. However, they would go on to lose to the Yankees in the 1999 World Series.