Floyd Mayweather and Conor McGregor finally fight on August 26 at Las Vegas' T-Mobile Arena in a light-middleweight match-up that has been building for over two years.
Here, Press Association Sport revisits the timeline of how a once-unlikely fight came to be made.
July 2, 2015 - Appearing as a guest on television programme Conan, Ireland's McGregor told host Conan O'Brien, referring to Mayweather: "I would box him if the opportunity arose."
December 30, 2015 - Mayweather responds for the first time, and their rivalry begins to grow, when he tells FightHype.com: "They say he talks a lot of trash and people praise him for it, but when I did it, they say I'm cocky and arrogant."
January 8, 2016 - On the suggestion they are treated unequally, McGregor, now 29, wrote on Facebook: "Don't ever bring race into my success again."
May 6, 2016 - Several months had passed in which McGregor even took to Twitter to insist he was retiring when it was reported the two were close to agreeing what would be a lucrative fight. However Dana White, president of the UFC, swiftly responded to insist: "It's not true."
May 8, 2016 - McGregor further raised the prospect of the match-up when, amid the build-up to Amir Khan's defeat to Saul Alvarez in Las Vegas, he wrote on Twitter: " MMA versus boxing."
May 13, 2016 - Mayweather responded by telling Showtime, the television network he has long fought on: "Hopefully we can make the fight happen. He's no pushover."
November 30, 2016 - Following six months in which many observers remained sceptical and suspected the publicity-hungry fighters were attempting to further build their already significant reputations, McGregor was granted a boxing licence in California.
January 11, 2017 - The public negotiations begin with Mayweather offering the Irishman 15million US dollars to fight him, and then White within 48 hours offering each fighter 25million US dollars.
February 15, 2017 - America's Mayweather, so often determined to remain in control of any significant announcements via social media, writes on Instagram: "There hasn't been any deal made in regards to a fight between myself and any other fighter."
February 16, 2017 - Mayweather starts as a 25-1 favourite to win the potential fight as the first betting lines come out.
March 8, 2017 - While in London to promote a fight between his protege Gervonta Davis and Britain's Liam Walsh, Mayweather tells McGregor via ESPN: "Sign the paper. You said you were the boss, just sign the paper and let's make it happen."
March 10, 2017 - Speaking on his Undefeated tour, Mayweather further builds excitement and speculation by saying: "I'm coming out of retirement just to fight Conor McGregor. Let's fight in June."
March 15, 2017 - White, also appearing on Conan and therefore almost bringing the saga full circle, says: "I do think it's going to happen. There's so much money involved, I just don't see how it doesn't happen."
April 16, 2017 - While posting an image of him wearing boxing gloves, McGregor writes on Instagram: "Join me in the preparation of my next fight, being announced very soon."
April 20, 2017 - He then posts another of him shadow boxing, with the caption: "Floyd may crap his jocks after all and if so I will go back to true fighting or just pick another boxer like Manny (Pacquiao) or something."
May 8, 2017 - McGregor and White agree terms to fight Mayweather, nearing the conclusion of the deal the Irishman has long pursued.
May 20, 2017 - Speaking at the post-Davis-Walsh press conference in London, Mayweather becomes the centre of attention and again talks up the possibility of the Mayweather-McGregor match-up.
May 21, 2017 - Despite a hope that they are nearing an agreement, McGregor writes on Twitter: "Sign your end Floyd or you are just a mouth."
June 5, 2017 - The biggest fight of 2017 between two professional boxers, Gennady Golovkin and Alvarez, is announced for Las Vegas' T-Mobile Arena on September 16, potentially affecting Mayweather-McGregor. The American has long favoured fighting in May and September, and the T-Mobile Arena has become Vegas' favoured fight venue.
June 14, 2017 - A boxing match between Mayweather versus McGregor is finally signed for August 26 at the T-Mobile Arena.
What are the differences between boxing and UFC
LENGTH AND NUMBER OF ROUNDS
A high-level boxing match is almost always scheduled for 12 three-minute rounds. When a boxer makes his professional debut, they are often scheduled for four three-minute rounds, which is usually gradually increased to six, eight, 10 and then finally 12. In women's boxing, two-minute rounds are largely favoured. Boxing debutant McGregor will fight over 12.
UFC rules dictate that each non-championship contest is to be scheduled for three five-minute rounds. A championship contest is for five five-minute rounds.
In both sports, there is a rest period of one minute between rounds.
THE NATURE OF THE FIGHT
Boxers are officially only allowed to attack their opponents through punching, and even excessive clenching is discouraged and monitored by the referee. If a boxer is knocked down, his opponent is not allowed to resume attacking him until he has returned to his feet and has the referee's permission to do so.
In UFC, fighters can box, grapple, wrestle, kick-box, and continue to strike their opponent while they have been knocked down.
SIZE AND SHAPE OF THE RING
A boxing ring, within the rules of the British Boxing Board of Control, should have four ropes and be between 16-20 square feet.
A UFC 'octagon' must be between a minimum of 20 square feet and a maximum of 32. It is also surrounded by a fence.
CUTS MEN
Boxers regularly provide their own cuts man, and one of their choosing. The UFC, however, provide one for each corner, and that same cuts man works the same corner for every fight of each event.
WEIGHTS
Boxing has more weight divisions than the UFC, and though many of those divisions share names, their weights vary.
The weight divisions in boxing are: minimum-weight 105lbs, light-flyweight 108lbs, flyweight 112lbs, super-flyweight 115lbs, bantamweight 118lbs, super-bantamweight 122lbs, featherweight 126lbs, super-featherweight 130lbs, lightweight 135lbs, light-welterweight 140lbs, welterweight 147lbs, super-welterweight 154lbs, middleweight 160lbs, super-middleweight 168lbs, light-heavyweight 175lbs, cruiserweight 200lbs, heavyweight over 200lbs.
UFC's weight divisions are as follows: straw-weight 115lbs, flyweight over 115lbs to 125lbs, bantamweight over 125lbs to 135lbs, featherweight over 135lbs to 145lbs, lightweight 145lbs to 155lbs, welterweight 155lbs to 170lbs, middleweight over 170lbs to 185lbs, light-heavyweight over 185lbs to 205lbs, heavyweight over 205lbs to 265lbs, and super heavyweight over 265lbs.
SPONSORSHIP
Unlike in boxing, UFC fighters are forbidden by their contracts to pursue their own sponsorship deals. They presently have an overall sponsorship in place with Reebok.
WEIGH-INS
In boxing, a fighter must weigh in at the scheduled time and if he or she is overweight, has an hour to return and achieve the correct weight. If they remain overweight after an hour they do not receive a further chance, though the fight may still proceed.
In the UFC, on the day before a fight, a fighter has a window of four hours in which they can make weight at their own convenience.
GLOVES
A boxing glove covers the entire hand, and in fights between the flyweight and welterweight divisions, 8oz gloves are generally worn.
In the UFC, a fighter's fingers remain exposed, and the glove generally weighs between 4oz and 6oz.
