NESTS is a rather secretive organization. Like a few others, NESTS is a means towards world domination. Of all the major groups involved in that 'race' however, NESTS is the least active in matters such as smuggling, drug trafficking, and so forth. Most of their funding comes from the talented scientists/researchers they recruit, as well as prize money from tournaments that their fighters are sent to compete in. They're probably even less known by the world at large than even "R" and Shadaloo are.
NESTS Cartel was created by Igniz, at first as solely a criminal cartel. Over the years, he came to desire godhood, and changed NESTS' focus. Recruiting talented genetic and cybernetic researchers through various means, Igniz planned to find out how to create the perfect human, or enhance an already existing one into perfection.
Realizing that if information about this research got out, that several groups would try to steal it away from NESTS, Igniz also recruited some talented fighters, such as Krizalid and Zero. These people would be tasked with keeping NESTS safe from enemies.
While methods such as abduction, brainwashing, and blackmail aren't totally out of the question when it comes to gaining new recruits to NESTS, Igniz usually doesn't have to resort to it. For all of his vile intentions, Igniz looks downright "heavenly", and has a notable talent for persuasion. Many people within NESTS firmly believe that Igniz is their friend, and that he has brought them together to improve mankind, for a better, brighter future.
The research in genetics and cybernetics has paid off, too. Some NESTS fighters, like Angel, have been left unaltered since they're already quite talented. Krizalid and Zero have been granted cybernetic battlesuits that improve their combat ability, and NESTS was also responsible for giving K' a functional copy of the Kusanagi bloodline flames. The truly incredible thing about that last part being that NESTS never succeeded in capturing Kyo for experimentation, and so they only had a little bit of his genetic material (gathered from fights he had been in), but still managed to use it to enhance K' in the correct manner.
They have even learned how to create cloned humans. Kula is an excellent example of this. She was 'born' with the power of ice within her, and wasn't born as an infant, but rather was already physically equivalent to a 14 or 15 year old girl, with roughly the mental capabilities of said 14-15 year old, and far superior physical abilities.
K9999 is another example of a 'homegrown' human being. While Kula is a relatively stable creation, K9999 was infused with too much power, and 'born' at too high an age to have really 'grown up' with the power, resulting in a somewhat unstable personality, as well as unstable control over his powers. As far as NESTS has come in these fields, they still have far to go.
Ultimately, cybernetics have fallen to a second-string research field for NESTS, used only when the situation calls for it; genetics has yielded far better results so far. And so NESTS continues to research, to grow, and plot.
While they have had some clashes with various groups, particularly the Syndicate and Shadaloo, none know where their hidden base is, and so for now, NESTS remains mostly safe, though sometimes their operatives are attacked in the field when recognized; a rare thing, given how secretive NESTS is.
NESTS has several unusual capabilities in the King of Fighters videogames, and they bear covering/summarizing here.
Cloning, "New Person" (KoF 2000, 2001): Kula falls under this category, as does K9999. "Cloning" in the sense that you're creating a whole new human being outside of the natural birth process is a relatively new field, but NESTS has shown fairly good competence at it. Such "new person clones" who aren't copies of any currently existing person are largely stable and healthy, as shown by Kula and K9999, though admittedly "stable" is relative in some cases.
Cloning, Copying Existing Person: Such as Kyo-1, Kyo-2, etc. in KoF 1999. In MotM's theme/storyline, such clones are unstable. They are, for all intents and purposes, nearly perfect copies of the person they aim to duplicate; same types of powers, a relative semblance of their personality, and an identical appearance. The problem is that these clones are of unstable health; NESTS has proven completely unable to produce a copy of an existing person, and have that copy live more than 48 hours. These "copy clones" just suddenly keel over and die. To date, NESTS has yet to figure out why.
Zero Cannon (KoF 2000): In the games, NESTS had a "Zero Cannon" which could vaporize cities from orbit. On MotM, they do not have this. They likely never will. Space technology in MotM's world is not as advanced as it is in the real world, nor even as advanced as it is in the videogames represented here.
NESTS' Space Station (KoF 2001): They also, in the games, had a space colony/platform they based their ultimate operations from. Not on here; MotM's world doesn't have the space tech to support something that grand.
Enhancing Existing Person: Such as the enhancements they may have done on Angel, Whip, and other people that were not created in NESTS' labs, but rather, taken there and improved. The effect this has tends to be very limited; NESTS just can't turn someone into Superman overnight, but can potentially help out a bit. Nonetheless, training and a drive to do well tend to be more helpful to the human body than NESTS gene therapy or any such things. Thus, the effects of such enhancement can have on MotM are, at best, minimal and downplayed, and worse, possibly outright useless in many cases.