That is what we discovered on Wikipedia relating to the HEX Struggle Collection:

Mixed martial arts (MMA) is a full-contact fighting sport based on striking and grappling, incorporating techniques from various combat sports from around the world.

In the early 20th century, various inter-stylistic contests took place throughout Japan and the countries of East Asia. At the same time, in Brazil there was a phenomenon called vale tudo, which became known for unrestricted fights between various styles such as judo, Brazilian jiu-jitsu, catch wrestling, luta livre, Muay Thai and capoeira. An early high-profile mixed bout was Kimura vs Gracie in 1951. In mid-20th-century Hong Kong, rooftop street fighting contests between different martial arts styles gave rise to Bruce Lee's hybrid martial arts style, Jeet Kune Do. Another precursor to modern MMA was the 1976 Ali vs. Inoki exhibition bout, fought between boxer Muhammad Ali and wrestler Antonio Inoki in Japan, where it later inspired the foundation of Shooto in 1985, Pancrase in 1993, and the Pride Fighting Championships in 1997.

In the 1990s, the Gracie family brought their Brazilian jiu-jitsu style, first developed in Brazil from the 1920s, to the United States—which culminated in the founding of the Ultimate Fighting Championship (UFC) promotion company in 1993. The company held an event with almost no rules, mostly due to the influence of Art Davie and Rorion Gracie attempting to replicate mixed contests that existed in Brazil and Japan. They would later implement a different set of rules (example: eliminating kicking a grounded opponent), which differed from other leagues which were more in favour of realistic, "street-like" fights. The first documented use of the term mixed martial arts was in a review of UFC 1 by television critic Howard Rosenberg in 1993.

Originally promoted as a competition to find the most effective martial arts for real unarmed combat, competitors from different fighting styles were pitted against one another in contests with relatively few rules. Later, individual fighters incorporated multiple martial arts into their style. MMA promoters were pressured to adopt additional rules to increase competitors' safety, to comply with sport regulations and to broaden mainstream acceptance of the sport. Following these changes, the sport has seen increased popularity with a pay-per-view business that rivals boxing and professional wrestling.