England's most prolific batter of all time defied Australia's all-pace attack at the Gabba in an unbeaten knock of 135 on Thursday.
It was all class. Once again Root, who came in at 2-5, was a rock around which his side's 9-325 by stumps was built.
It was the 34-year-old run machine's 40th Test hundred and fifth against Australia, compiled in the most difficult of conditions in a treacherous pink-ball, day-night arena where only the best prevail.
Root's highest score in Australia previously had been the 89 he posted four years ago at the Gabba, when a thin edge off Cameron Green brought him unstuck with the elusive milestone in sight.
He was not to be denied on this occasion, despite a mix-up with Ben Stokes (19) in the post-dinner break that was swooped upon brilliantly by Josh Inglis to complete a stunning run-out of the captain.
Runs all of a sudden dried up for a short period, but Root swayed back to late-cut Brendan Doggett for four to move into the 80s. Two pulls to the boundary off the same bowler got him to 96.
The Barmy Army's "Rooooooot" call reached a crescendo when he turned Scott Boland to the fine-leg boundary and notched three figures.
He removed his helmet, kissed it and then blew on his gloves before giving his teammates, in rapturous applause, an unassuming shrug to say, 'it's done'.
Root had a willing ally initially in opener Zak Crawley, who made a typically breezy 76 after bagging a pair in Perth. The pair combined for a 117-run stand for the third wicket and played with confidence in the daylight hours.
Crawley was in awe of his countryman and hailed the century as one of his best, with the pressure of the match situation and history on Root.
"I forget some of his hundreds. That is how many he has got," Crawley said.
"It is a phenomenal knock. It was doing plenty when he first came in but he was so calm and clear about how he wanted to go about it.
"When you put everything into consideration, it has to be one of his best.
"We were talking about it for ages before he got there and then he got there and we were chuffed for him ... and so was everybody in the ground. It was a great moment.
"Everyone sees his talent but no-one sees the inner steel."
Root had the rub of the green that all batters who make Test centuries need in the course of an innings.
When on two he was squared up by a Mitchell Starc delivery that bent away and the edge just eluded a diving Steve Smith at second slip and raced to the boundary.
On 62 he survived an lbw review, which showed Scott Boland's nip-backer was just going over leg stump.
Between all that, he played late, left well and drove beautifully.
His on-drives were sumptuous, with seven boundaries struck in the arc from mid-off to wide mid-on.
Root also proved to be king of the night-time world in a dazzling unbroken 61-run partnership for the last wicket with Jofra Archer (32no) from just 44 deliveries. The fast bowler notched his highest Test score in the process.
"We definitely won that last hour," Crawley said.
"They are valuable runs. I think anything above 300 is a good score."
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