Celtic have put an end to Manchester City's 10-game winning streak and manager Pep Guardiola's perfect record, with a 3-3 draw in their Champions League match at Celtic Park.
City had to come from behind three times to earn the draw, with the home side's Moussa Dembele scoring at the start of each half and Raheem Sterling netting a first-half own goal for the Scottish champions.
Celtic were unrecognisable from the side that was humbled 7-0 at Barcelona in their opening game.
But City simply refused to be subdued, responding with strikes from Fernandinho, the excellent Sterling and Nolito and coming close to a late winner that would have equalled Tottenham Hotspur's 11 straight wins in 1960-61 as the best start to a season by any English club.
City move into second place in Group C on four points behind Barcelona, who won 2-1 at Borussia Moenchengladbach.
Meanwhile Arsenal beat FC Basel 2-0 after Theo Walcottt scored twice before halftime at Emirates Stadium to move joint top of Group A.
The England forward twice combined brilliantly with Alexis Sanchez as Arsenal overwhelmed the Swiss to stretch their unbeaten run in all competitions to eight matches.
Arsenal were brimming with confidence from the start on the back of a 3-0 defeat of Chelsea at the weekend while Basel had won 11 of their 12 matches this season.
Bayern Munich's perfect start to the season under coach Carlo Ancelotti came to an end as Atletico Madrid managed a 1-0 home victory.
Bayern were aiming to make it nine wins in a row in all competitions, but were derailed by an Atletico side that took a deserved 35th-minute lead courtesy of Jannick Carrasco, and remain unbeaten this season.