It all began in 2002, back when the Rams were in St. Louis and the Patriots were a plucky underdog standing in the way of a potential dynasty.

So much has changed.

This hasn’t: Bill Belichick and Tom Brady.

The duo, every bit as formidable now as when they won that first title, face the Rams, now back in Los Angeles, in a Super Bowl rematch of sorts that pits the NFL’s past against its future.

At 32, Sean McVay is the youngest Super Bowl coach. At 66, Bill Belichick has an NFL-record 30 playoff wins.

At 24, Jared Goff is the youngest quarterback to win the NFC championship. At 41, Brady will be the oldest quarterback to start a Super Bowl.

The Rams (15-3) are back in the Super Bowl for the first time since that meeting against the Patriots — and for the first time as the “Los Angeles Rams” since 1980, when they fell to the Steelers. The Patriots (13-5) are back for the third straight time, the fourth in five years and the ninth since Belichick got the dynasty on track in the 2002 win over St. Louis.

The Rams duo of McVay and Goff has spent the past two seasons heralding the coming of a new age of football — one in which McVay’s reimagined offense has dealt a blow to the old, increasingly dated adage that teams ultimately must win championships with defense. The Rams have cracked 30 points in 13 of their 18 games this season.

But to officially usher the NFL into a new era, the Rams will have to get past New England, which is a 1-point underdog for the game in Atlanta, set for Feb. 3 — exactly 17 years to the date of the last Super Bowl showdown.

Is Brady up to it?

Well, on Sunday, he drove the Patriots down the field for three straight touchdowns — two in the fourth quarter and once in overtime — for a 37-31 victory over the Chiefs, the only team that outgained Los Angeles this season.

We get a “rematch” of that 2002 Super Bowl, won by the Patriots 20-17.

The Rams came into that game as a franchise on the edge of a dynasty.

They were one season removed from their first Super Bowl win, led by quarterback Kurt Warner and known as “The Greatest Show on Turf” for the fake grass they burned up at their seven-year-old home in St. Louis. They had amassed what was then unheard of — 500-plus points in three straight seasons.