Pedro got Chelsea's away goal, having scored twice against Slavia Prague in the previous round
Pedro scored an away goal as Chelsea recovered from an early setback against Eintracht Frankfurt to set up an exciting Europa League semi-final return leg at Stamford Bridge.
Eintracht took the lead through their top scorer Luka Jovic, who superbly steered in Filip Kostic's ball.
The Blues, who started with Eden Hazard on the bench, equalised when Pedro thrashed home just before half-time.
David Luiz also went close when his dipping free-kick came off the bar.
The draw means that Chelsea become the first team to go 16 successive Europa League matches without defeat, breaking the record set by Atletico Madrid from 2011 to 2012. They will have the chance to make it 17 in next Thursday's second leg.
Did leaving Hazard on the bench pay off?Eden Hazard, who has scored 19 goals for Chelsea this season, has yet to find the net in the current Europa League campaign
There was a great deal of surprise when the Chelsea team-sheet showed Hazard's name among the substitutes.
Manager Maurizio Sarri told BT Sport that he rested his 19-goal forward because of fixture congestion, with the Belgian having played 10 matches in a row. So it was a penny for Hazard's thoughts when he was shown watching his team struggle and a goal down after 23 minutes.
However, Sarri did not rush on his key attacker and instead kept faith with what he had on the pitch, and was repaid with an excellent display thereafter.
Ruben Loftus-Cheek, brought back into the XI, led the fightback. After Pedro went close with a strike that drifted past Kevin Trapp's left-hand post, the England player kept the goalkeeper on his toes with a strike that also flirted with the woodwork.
The pair then combined for the goal. Eintracht's defenders lost possession after dawdling on the ball in the area, and Loftus-Cheek carved out an opening for Pedro to do the rest.
The Blues midfielder went close twice more, first with an effort that swept over the bar and then with a stinging shot with the outside of his boot that tested Trapp.
Brazilian Luiz went even closer with an blockbuster of a free-kick that dipped wickedly and crashed off Trapp's bar. Hazard, who came on in the 61st minute, then set up another opportunity for the defender, but this time he headed straight at the German keeper.
They should have won the game but will no doubt be content with how they began their ninth major European semi-final since the Roman Abramovich era began in 2003. A repeat display at Stamford Bridge should see them reach their sixth European final.
Eintracht tire after bright openingSerb Luka Jovic has been linked with a move to Real Madrid
Prior to kick-off, Eintracht supporters produced a spectacular display by holding up black and white cards in the team's colours, while at one end a giant tifo covered the entire stand.
Coach Ade Hutter's team lived up to the lavish introduction in the opening half hour, and underlined why they were unbeaten in 11 home games in the competition.
Key to their success so far has been the forward combination of Kostic and 21-year-old Serb Jovic, who is likely to be courted by several top European sides in the close season.
Jovic has been in outstanding form this season, during which he made his move from Benfica permanent, and gave Bundesliga's fourth-placed side the lead with a deft header from Kostic's delivery.
However, as Chelsea grew into the match, his team-mates appeared to lose their way. Eintracht's only clear-cut chance after the break fell to captain and defender David Abraham, who headed over from eight yards.
