Max Verstappen's first Monaco Grand Prix victory has put him into previously uncharted territory in Formula One -- he now leads the world championship.
His flawless and dominant performance came as Ferrari let a golden opportunity slip through its fingers, while Mercedes drivers Lewis Hamilton and Valtteri Bottas both had races they will want to forget in a hurry.
Here's a look at the main talking points from Monte Carlo.
Red Bull go top
For this first time since 2013, Red Bull is leading both the drivers' and constructors' championships.
Max Verstappen's victory in Monaco provided an 18-point swing against Lewis Hamilton's seventh place and fastest lap, meaning he now has a four-point lead over the reigning champion after five races, while Red Bull took 30 points out of Mercedes, giving it a one-point lead in the constructors'.
Effectively, the tallies have been set to zero -- or near enough -- with just over a fifth of the season done.
Any concerns that Mercedes and Hamilton were about to kick-on and disappear towards an eighth championship have been allayed, while Verstappen's record of finishing in the top two at every race in 2021 rolls on.
For all its success in recent years, Mercedes has been prone to the odd horror weekend -- Bahrain 2020 and Germany 2019 spring to mind -- and Monaco 2021 was no different.
It's important to remember that Mercedes was far from happy with its car just two months ago when it first tested in Bahrain, and it seems that, in certain circumstances, not all of the creases in its performance have been ironed out.
But that should not take away from Red Bull's second victory of the season and the near faultless performance of Verstappen over the weekend.
Monaco has been a Red Bull stronghold for some time now: in 2016, Daniel Ricciardo should have beaten Lewis Hamilton to victory here, in 2018 he did and in 2019 Max Verstappen looked like the fastest driver in the race but was bottled up behind Hamilton.
But as prestigious as a win in Monaco is, the circuit is still an anomaly on the F1 schedule and success on the streets of Monte Carlos is no guarantee of success at the majority of other circuits on the calendar.
That helps to explain why Ferrari was suddenly a front runner in Monaco after spending the previous four races adrift of Mercedes and Red Bull.
But in a season as tight as this, both Mercedes and Red Bull will have highlighted must-win races -- the ones where the strengths of their car are flattered by the circuit layout and the weaknesses are hidden.
Monaco was one such circuit for Red Bull.
"It was important to take our chances here," Red Bull team boss Horner said. "Mercedes had a rare off weekend and it was important to convert that.
"We leave here leading both championships for the first time in the hybrid era, and so that's really encouraging.
"No one I getting carried away, there is an awfully long way to go, but to be as close as we are is encouraging."
Likewise, there will be circuits where a poor result is more acceptable as it represents fewer lost points relative to the potential of the car, and it's clear that Monaco exposed some of the Mercedes' weaknesses.
"We were always on the backfoot, it seems to be a kind of cursed race track for us," Mercedes team principal Toto Wolff said. "It's a little bit like Singapore where we never got down to [understanding] the problems until very late.
"When you start on the backfoot and have no grip and no trust in the car, it's very difficult to recover.
"Overall a weekend to forget -- well not to forget, because tomorrow we're going to put the finger in where it hurts most and try to learn."
Mercedes is clearly not happy with its Monaco Grand Prix weekend, but it will take some comfort from knowing it scored points at races earlier in the season where Red Bull appeared to have the stronger package.
The championship was not won or lost in Monaco, but it helped develop the picture of how it might be later in the year.
What's clear is that the title race is very much on.
What went wrong for Hamilton?
Seventh place was not what Lewis Hamilton had in mind as he descended from the 30th floor of his Monaco apartment block on Sunday morning and hopped on his personalised motorcycle to commute to the track.
It's not what he had in mind as he sat with his engineers discussing how a longer first stint than his rivals might result in an opportunity to move up a couple of places from his starting position.
And it was certainly not what he had in mind as Pierre Gasly emerged from his own pit stop ahead of him, followed by Sebastian Vettel a lap later and Sergio Perez four laps after that.
So what went wrong?
The quick answer is tyres. But as is so often the case in Formula One, it's not that simple.
In qualifying, Hamilton was struggling to get enough temperature in his front tyres to induce the necessary chemical reaction in the rubber that would allow him to access the true potential of his Mercedes car.
Teammate Valtteri Bottas -- using a very similar setup -- more or less managed it, but Hamilton only really got close when he was on his final flying lap, just as the red flags came out for Leclerc's accident and he had to back off.
He had suggested a way of getting more heat into the tyres to his team after Thursday practice, but his engineers had been reluctant to follow his advice.
In the world of engineering, nothing comes for free and there was a danger that the extra performance in qualifying would have significantly worsened his performance in the race.
Perhaps that would have been the way to go given the end result, but the whole reason Hamilton's race strategy didn't work on Sunday was because his tyres were experiencing more wear than those of his rivals, forcing him to pit earlier and costing him performance.
Once he had pitted, he then couldn't get the necessary temperature in his new tyres to find the performance difference he needed to pass Gasly.
And once behind Gasly, the pace was so slow he was unable to fend off the superior strategies of Vettel and Perez.
He was vocal over the car-to-pit radio, but both he and the team know the problem was not the strategy itself, but the overall performance of the car in Monaco.
Hamilton has already made time in his diary for a series of engineering debriefs next week, which he hopes will provide answers that could benefit him later in the year.
As he returned to his Monaco apartment on Sunday evening, however, he may have taken some comfort in the knowledge that his engineers are among the best in the business at solving such issues.
Heartbreak for Leclerc
Make no mistake about it - the 2021 Monaco Grand Prix was Charles Leclerc and Ferrari's to lose.
And lose it they did, before the race had even started.
Pole position was impressive, but his heavy crash into the barriers at the end of qualifying left doubts about his car which lingered into Sunday. Ferrari declared ahead of the race its investigations had shown no damage to the gearbox and that no changes were required - in other words, the team was avoiding the five-place penalty normally associated with changing that part of the car.
Leclerc knew almost as soon as he drove the car out of the garage there was an issue. You know the story by now - the race started with the pole position slot empty as Leclerc and Ferrari were unable to fix his car in time for the start.
It was easy to assume Ferrari had simply gambled and lost, banking on the damage being manageable on a circuit where track position is king.
Ferrari remains uncertain about exactly what caused the driveshaft failure, but team boss Mattia Binotto suggested the two things were unrelated.
"The failure is on the driveshaft into the hub on the left-hand side," Binotto said after the race. "So it's not a gearbox problem we had. The gearbox had been inspected yesterday evening, it has been reviewed, and I think the gearbox was OK for the race.
"What happened is on the opposite side compared to the accident. So it may be completely unrelated to the accident.
"But something which we need to carefully understand and analyse, and we have no answer right now."
The results of Ferrari's investigation will be intriguing.
Whatever they find, it won't change anything for Leclerc. He's never finished his home race and this felt like an especially cruel slice of bad luck for a driver who has been so consistent for Ferrari during what has been a bleak spell in its Formula One history.
There was a slice of fortune to pole position, given how qualifying finished, but there's no guarantee the order would have looked any different had everyone finished their final attempts. At a circuit like Monte Carlo, that early Q3 banker lap is key.
Leclerc is good enough that he will surely have chances to win the Monaco Grand Prix again, but this one will surely leave a sour taste for a long time.
Monte Carlos Sainz
Ferrari will see this is a race victory that got away, but Carlos Sainz at least managed to salvage something positive for the team with its first podium finish of the season.
Sainz still wasn't entirely happy with second. Like Max Verstappen, Sainz felt Leclerc's late crash had ruined a lap quick enough to be on pole position, and he had to settle with starting from fourth (which effectively became third after Leclerc failed to start).
He inherited second position when Valtteri Bottas suffered cruel misfortune of his own midway through the race but was still left wondering what might have been had things all played out differently.
"It is a good result," Sainz said. "I mean, if you had told me before coming to Monaco that I would have finished second, I definitely would have taken it.
"The whole circumstances of the weekend - having Charles on pole, me missing out in qualifying yesterday on a good lap - it maybe doesn't taste as good as it should. But I'm sure when I reflect back on the weekend, I'll be very happy and proud of the weekend. I think Ferrari, as a team, they need to be proud about the car and the step they've done this year."
Sainz has, very quietly, been pretty impressive at Ferrari this year. Many people underestimated Sainz and thought he might be exposed alongside Leclerc at Ferrari.
While Leclerc has been the stronger and more consistent performer of the two, Sainz has adjusted to his new environment very well so far - much quicker than race winners Sergio Perez and Daniel Ricciardo and two-time world champion Fernando Alonso have to their own respective car changes.
Binotto said Sainz's performance is the type of thing Ferrari expected when they picked him to replace Sebastian Vettel this season.
"I think [it shows] he's a good driver and we knew it -- we employed him!" Binotto said.
"I think he is showing how good he is. It's good for Ferrari that we made the right choice with him, we are pretty happy.
"He's integrating very well, he's driving fast, he's a good leader inside the cockpit but also outside. I think he's a good benchmark for Charles, he's pushing Charles to do better and that was the objective."
Bottas can't catch a break
Leclerc's misfortune was difficult to watch, but Valtteri Bottas was just as unfortunate with how his Monaco Grand Prix unravelled.
Bottas has picked up plenty of flack over the past few seasons for sub-par performances but this was not one of them.
He out-performed Lewis Hamilton all weekend and had been just 0.03s off second on the grid - a grid slot which, it turned out, would have given him a clear run to Turn 1 on Sunday afternoon.
The Finn looked good for second position until his pit-stop, when Mercedes could not remove his front right tyre from the car at what should have been a routine change.
Mercedes later explained that the wheel nut had machined onto the axle -- unbelievable bad luck for a driver already on the back foot at this stage of the season.
The issue eventually prompted Bottas to retire from the race and that meant talking to the TV cameras while the race was still going on.
"I couldn't believe what was happening and it still feels strange now that the others are racing there and I'm here, but it happened," he said.
"It was a big mistake by us, as a team, to learn from. Either if it is human error or a technical issue, it doesn't matter, we need to find the solution.
"If it's a human error, we need to support the guy who did it, but we need to learn from that - that's the main thing in my mind. And, at the same time, I'm super disappointed."
After five races, Bottas is fourth in the standings, behind Lando Norris. He is already 58 points behind championship leader Max Verstappen.