A brace from Kaka and a goal from the promising teenager Bryan Cristante assured Milan of the much-needed three points which move them up the Serie A table.
It was perhaps Milan's best display this season, an aesthetically pleasing performance doubled by solid defensive work from a usually porous back line.
Without further ado, let's take a look at five things we learned from this pivotal Serie A encounter.
An 18-year-old making only his second appearance for Milan in Serie A shouldn't have done what he did.
Cristante's midfield presence invigorated a Rossoneri side that has so often looked flat through the course of the season.
His box-to-box tenacity and forward runs into the opponents' penalty area were those of a wily veteran, not an inexperienced youngster.
Adding to his creativity, Cristante hit the woodwork in the first half and scored from outside the box when he struck a missile into the bottom left corner.
Teammates swarmed to hug him following his goal, and it's not crazy to assume that he'll get another starting nod next week until the reality of the situation catches up with him.
It was only a day ago that Milan were five points above the relegation zone, but a vital three points and a slew of January transfer signings and rumors have injected new life into the wounded club.
A once proud symbol of football has been jeered and scoffed at, but there is still time to make a dramatic comeback and reach the top five.
Milan now have 22 points after 18 rounds of action, putting them 10 points below fifth-place Hellas Verona.
If last season is any indication, expect a massive comeback from the Rossoneri.
Atalanta's most prized possession is perhaps young midfielder Giacomo Bonaventura.
The Bergamo No. 10 likes to play on the left-hand side of midfield where he can take on his defender and either send in crosses or make his way into the box where he has good finishing ability.
The 24-year-old has been on the radar of some of Italy's giants, including Milan. Needless to say, it'll be very hard for Atalanta to hold on to his services as his star grows brighter every week.
Kaka scored his 100th and 101st goals for Milan against Atalanta.
The first was a fantastic solo effort where he was able to slide the ball past Atalanta goalkeeper Andrea Consigli from an acute angle. Shortly after the goal, he held up a jersey showing his new achievement.
The second goal was more of a tap-in from close range, but Kaka showed his anticipation and predatory instinct in the box by cleaning up after Robinho's botched stop.
It's incredible that he's been able to perform at such a high level after being rarely used in three seasons at Real Madrid, and he has proved many of his doubters wrong by excelling for Milan and being a consummate professional.
If 2014 didn't get off to a good start already, Milan fans also have the pleasure of seeing Japanese playmaker Keisuke Honda debuting next week when they take on lowly Sassuolo.
Honda was in attendance at the San Siro to witness the shellacking put on by his new club and will surely offer a helping hand to the attack to give them another gear.
Keisuke is expected to play in a Christmas tree formation alongside Kaka, as they both hover around Mario Balotelli.