Henrik Larsson's 35th European goal for Celtic ensured the scores were level after the Uefa Cup quarter-final, first leg tie against Villarreal.
The Spanish visitors took an early lead with a Josico header and enjoyed most of the possession in the first half.
Celtic survived a few scares before Larsson headed home a cross from Didier Agathe in the 64th minute.
Larsson had the ball in the net ten minutes before the goal but the striker was penalised for handball.
Celtic made a bright start, moving the ball around slickly on the newly relaid surface and forcing their opponents to defend from deep.
But the noisy home fans were stunned in the ninth minute when Garcia Roger's cross grazed the head of Josico and the ball drifted into the corner of the net.
A few minutes later Brazilian striker Sonny Anderson broke clear of the Celtic defence and shot narrowly wide from 20 yards.
Celtic lost their early fluency but passed up a great chance to level after 19 minutes when Chris Sutton's accurate centre was headed over the crossbar by Stilian Petrov from eight yards.
With Roger and Juan Roman Riquelme pulling the strings from midfield, Celtic were denied possession for long spells as the visitors grew in confidence.
But Petrov again found room behind the Spaniards' defence and his fierce volley was tipped on to the post by Jose Reina.
Seven minutes from the interval Anderson sent Jose Mari scampering into the Celtic penalty box but the Spanish international shot high over the bar.
In the final minute of the first half Sutton and Larsson combined well but the English striker's low, angled strike was comfortably held by Reina.
Early in the second period Alan Thompson's cross broke invitingly for Larsson 15 yards from goal but Rodolfo Arruabarrena managed to block the striker's shot.
Soon after, the Celtic defence was ripped open as Anderson ran on to a Riquelme pass but teenage keeper David Marshall made a fine block.
From the resulting corner the ball was worked out to Sebastian Battaglia, who saw his thunderous a 22-yard strike clip the crossbar.
Celtic were then controversially denied an equaliser when Larsson charged down Reina's attempted clearance and the ball flew into the net.
Referee Kyros Vassaras signalled a goal but the linesman flagged for handball, which seemed harsh given the ball was cannoned at Larsson from just a few yards.
However, Celtic did not have long to wait for a goal and it was Larsson who rose to meet Agathe's cross before the advancing Reina and nod the ball into an empty net.
A great cut-back from Stephen Pearson found Larsson lurking on the penalty spot but the Swede scooped his shot over the top.
In the 83rd minute Reina produced a wonderful diving save to push away Agathe's low strike and from the following corner the keeper did well to hold a header from Stanislav Varga.
In time added on, Reina spilled a free-kick from Larsson but recovered to block Sutton's close-range effort and Agathe's follow-up header was cleared off the goal-line by Sergio Ballesteros.
Celtic: Marshall, Agathe, Balde, Varga, McNamara, Petrov, Lennon, Pearson (Miller 79), Thompson, Larsson, Sutton.
Subs not used: Douglas, Valgaeren, Lambert, Mjallby, Beattie, Smith.
Booked: Pearson, Larsson, Thompson.
Villarreal: Reina, Javi Venta, Ballesteros, Coloccini, Arruabarrena, Josico (Marti 78), Riquelme, Roger, Battaglia, Jose Mari, Anderson.
Subs not used: Lopez Vallejo, Victor, Quique Alvarez, Calleja, Arzo, Verza.
Booked: Josico, Roger.
Referee: Kyros Vassaras (Greece).