A beginners' guide to the UFC and the world of the octagon
The UFC is the largest mixed martial arts competition in the world.
The cage - known as the octagon - has eight sides which create wide angles to prevent the fighters from becoming stuck in a corner.
In the very early days of the UFC, when few rules applied, a US senator led a successful campaign against the sport, resulting in the sport being banned in a 36 US states.
UFC matches may end by knockout, technical knockout - where the referee decides a fighter cannot continue - submission - when one fighter taps out or verbally submits - by judges' decision, disqualification, forfeit or no contest.
UFC fighters will generally be paid by the fight, with amounts depending on their public profile. Fighters do, however, receive substantial financial bonuses if they win fights, with cash bonuses also awarded for 'Fight of the Night' and 'Performance of the Night'.
On November 16t, 2012, the UFC signed its first female fighter, former Olympic Judo medalist Ronda Rousey.
Irish UFC contender Aisling Daly is currently taking part in the hit TV reality series The Ultimate Fighter, which follows 16 pro-female fighters battling it out for the UFC's first ever strawweight (115 pounds) championship belt.
Tonight Conor McGregor faces Dustin Poirier. Cathal Pendred will fight Gasan Umalatov on October 4 in Stockholm and Paddy Holohan takes on Louis Gaudinot in Canada.