Hannover moved back up to seventh in the Bundesliga with a stylish win over relegation-threatened Cologne.
Lars Stindl put Hannover in front in the 19th minute, but Cologne levelled deservedly two mintes before the interval through Kevin Pezzoni.
The game was on a knife edge and Cologne missed several excellent chances before Jan Schlaudraff put the home team in front from the penalty spot.
A brace from Mame Diouf then sealed Hannover's win to take them to within a point of sixth-placed Werder Bremen.
There were good early chances for both sides with Konstantin Rausch shooting across goal and then Milivoje Novakovic and Mikael Ishak both missing for Cologne.
Stindl put the Reds in front in the 19th minute as he reacted quickest when Schlaudraff's shot was only parried by Michael Rensing, and Stindl was a touch fortunate too as he got a favourable rebound off the Cologne goalkeeper to give him a simple tap-in.
Both sides continued to attack in an entertaining game and Mohammed Abdellaoue and Manuel Schmiedebach both missed chances in quick succession as Hannover looked to add to their lead.
Stindl's 35th-minute effort from 25 yards just missed the post by inches before, at the other end, Clemens brought a fine one-handed save out of Ron Robert Zieler to force a corner, from which they levelled.
Pezzoni, wearing a mask due to a facial injury, bravely put out his head to divert the corner in at the near post.
The second half was equally exciting with Diouf going close to making an immediate impact following his arrival at the break, but he was unable to make contact with cross from the right at full stretch.
Ishak hit the post and Novakovic missed two gilt-edged chances for Cologne to take the lead before Hannover regained the advantage from the penalty spot.
Rausch went to ground amid a tussle with Henrique Sereno and Schlaudraff stepped up to place the spot-kick in.
Rausch missed a one-on-one as Hannover, rather than sitting on their lead, tried to increase it.
They managed that in the 67th minute when substitute Didier Ya Konan broke down the right and squared the ball to Diouf, who seemed to waste the chance when he brought the ball back inside, but he threaded his shot through Rensing's legs.
Ya Konan and Diouf missed two more one-on-one chances before Diouf rose to head in from a corner and seal an emphatic win for the Reds.