A stunning strike from Arjen Robben fired Bayern Munich into the quarter-finals of the Champions League on away goals at the expense of an unlucky Fiorentina at a wet and windy Stadio Artemio Franchi.
The Germans, leading 2-1 from the first leg, were second best for long periods of the game and had looked to be on their way out of the competition when Juan Vargas and Stevan Jovetic scored the game's opening two goals to put the hosts ahead in the tie for the first time.
But Jovetic's strike sparked a manic 11-minute period during which four goals were scored and Bayern took an unlikely grip on the game.
Van Bommel levelled the tie with a low drive on the hour only for Jovetic to score his second four minutes later.
That sparked wild celebrations from the home bench, but just 72 seconds later Robben, who had been well marshalled until that point, broke free of his markers to unleash an unstoppable 30-yard strike to settle the contest on away goals.
Bayern boss Louis van Gaal handed 17-year-old David Alaba a first start as a makeshift left-back in place of the injured Diego Contento while Robben returned after recovering from a cold.
The home side had the advantage of a strong wind at their backs in the first half and Vargas tried to make use of it early on with an ambitious 40-yard free-kick that just flew over.
The Peruvian was an early menace and his cross soon after appeared to strike Daniel van Buyten's hand in the penalty area, although the home side did not make much of their appeal.
In the 22nd minute Bastian Schweinsteiger earned a caution that will rule him out the first leg of Bayern's quarter-final after he fended off the chasing Jovetic with a hand to the face.
Fiorentina went ahead in the 28th minute when Vargas pounced on a weak clearance from Bayern goalkeeper Jorg Butt and found the net with an expert finish under pressure from a tight angle.
Bayern then lost striker Mario Gomez to a leg injury on the half hour with Miroslav Klose his replacement.
The Germans should have gone level after 34 minutes when the ball broke for Robben who blasted a shot from 12 yards only to see Sebastian Frey make a superb reaction save.
It was a rare attack for Bayern whose forward threat was effectively snuffed out by the hosts who consistently double marked wingers Robben and Franck Ribery to cut the supply.
Fiorentina's grip on the game strengthened further when Jovetic fired home after 54 minutes, following a superb backheel from Alberto Gilardino, to send the hosts 3-2 ahead on aggregate.
But the match was turned on its head in the next 11 minutes as the goals flew in.
Bayern grabbed their lifeline on the hour when Ribery outpaced three markers before sliding a pass to the top of the area where Van Bommel drilled a low shot in at the left post.
Four minutes later La Viola were ahead in the tie again when Gilardino again fed Jovetic, this time with a header, and the young Montenegrin outmuscled Van Buyten and forced home from close range.
Fiorentina's celebrations showed they thought they had done enough, but just a minute later they were staring elimination in the face when Robben cut inside before unleashing an unstoppable drive that flew in the top-left corner from 30 yards.
Fiorentina still had plenty of time to find a reply, but now deflated they never threatened to find a way back into the game.
