Heart of Midlothian secured a historic victory in the east end of Glasgow on Sunday, defeating Celtic 2-1 to go three points clear at the league summit.
After a rocky opening where the Jambos absorbed a mountain of pressure, Claudio Braga struck right before the half's end to secure Hearts a surprise lead against the run of play.
After that, the Jambos gained a foothold, and began to roar back, culminating in a stunning second half header from Oisin McEntee - with a late strike from Kieran Tierney not enough to undo the Jambos' work.
Derek McInnes made four changes to the side that was held at Fir Park last weekend; Michael Steinwender, Craig Halkett, Claudio Braga, and Oisin McEntee all returning to the fray as the Hearts boss opted for a three man midfield.
Celtic, in their first match under the reign of new boss Wilfried Nancy, fashioned two big chances after nine minutes, Daizen Maeda nearly notching on both occasions.
The Japanese forward first fluffed his lines with a scuffed shot after a sharp through-ball from Kieran Tierney split the Jambos open, before poking wide moment later by a matter of inches - a good diagonal from Callum McGregor was knocked into his path by Sebastian Tounetki.
The hosts were well up for it, and Michael Steinwender did well to divert a Tounetki effort into the side netting after 17 minutes following some tricky footwork to cut in to the Hearts area on the left side.
After 30 minutes, the boys in maroon still hadn't been able to get their foot on the ball and do anything on their terms, with Celtic seeing another chance go astray after Steinwender's clearance was met on the volley by Arne Engels - the Belgian's rocket going high and wide over the bar.
With half-time approaching, Hearts raced into an extraordinary lead against the run of play.
Lawrence Shankland did so well to make it to the byline and whip a cross in. Harry Milne's mishit fell into the path of Claudio Braga and, with Celtic anticipating an offside flag that never came, the man from Porto was able to tuck the ball home and hand Hearts an unexpected lead.
HT: Celtic 0-1 Heart of Midlothian
It was going to be a long second 45 for Hearts, and Celtic came out swinging - Maeda laying the ball into the path of Engels after 51 minutes, but his lofted effort from close range was over the bar.
Callum McGregor was next to try his luck on 56 minutes, sending a low strike towards the bottom corner from distance, with the excellent Alex Schwolow throwing himself down to gather the ball.
Hearts weren't without their moments, and went agonisingly close to a second after a good cross from Shankland almost picked out Tomas Magnusson in the middle, but the Icelandic midfielder wasn't able to get his head to it.
Another chance fell the Jambos' way on 64 minutes as Kyziridis sent Shankland into the box, but his slam at goal was beaten away by Kasper Schmeichel as the boys in maroon began to tighten their grip.
Hearts' second arrived shortly after, and what a goal it was.
Harry Milne's corner was whipped into the box at breakneck speed, with Irish midfielder Oisin McEntee peeling away from his marker and planting a powerful head on the ball, looping over the Celtic 'keeper and in to send the maroon corner of Parkhead into raptures.
With just minutes to go, and a desperate fight to secure the three points, Alex Schwolow produced a world class save to deny Celtic a goal, standing firm to tip a diving header from Engels away at point blank range before Daizen Maeda smashed the ball off the crossbar on the rebound.
The Jambos would hold on though, and not even a late goal from Kieran Tierney was enough to undo the afternoon's work, as the Jambos secured a valuable three Premiership points.
Celtic: Schmeichel, Scales, Trusty, Nygren (Kenny 64'), Yang, Tounekti (McCowan 58'), Engles, Maeda, Hatate, McGregor, Tierney
Subs: Sinisalo, Balikwisha, McCowan, Iheanacho, Kenny, Bernardo, Murray, Donovan, Ralston
Hearts: Schwolow, Halkett (Kent 77'), Shankland (Borchgrevink 85'), Braga (Kabore 77'), Devlin, Steinwender, Milne (Kingsley 71'), Findlay, Magnusson, McEntee, Kyziridis (McCart 71')
Subs: Gordon, Kent, Kingsley, McCart, Kabangu, Kabore, Borchgrevink, Spittal, Kartum
