S.H.I.E.L.D

S.H.I.E.L.D. is an espionage and law-enforcement agency created by Stan Lee and Jack Kirby in Marvel, it often deals with paranormal and superhuman threats.
It stood for Supreme Headquarters, International Espionage, Law-Enforcement Division.
Then it changed to Strategic Hazard Intervention Espionage Logistics Directorate in 1991.
Colonel Fury was reimagined as a slightly older character with an eyepatch which he lacked in his wartime adventures and appointed head of the organization.
Its most persistent enemy is Hydra, a criminal organization founded by Baron Wolfgang von Strucker.

S.H.I.E.L.D. was presented as an extant, full-blown entity in its first appearance, with Tony Stark in charge of the Special Weaponry section and Fury seeing "some of the most famous joes from every nation" at a meeting of the Supreme International Council.



Fictional history
Usually Nick Fury is the executive director, S.H.I.E.L.D. has been depicted as an organ of the United Nations with U.N and it have vast technological resources at its disposal.

S.H.I.E.L.D. first come up as a top secret international organization  with the Supreme International Council made up of top officials and minds from across the world, including Tony Stark the Iron Man.
Its first director was Rick Stoner, former head of the CIA, but he was quickly assassinated by Hydra, and the President of the United States recommended Nick Fury to take his place.
The ultimate authority of S.H.I.E.L.D. is a cabal of 12 mysterious men and women who give Fury orders and operational structure, leaving Fury to manage the actual implementations.

 LMD (Life Model Decoy) is one of S.H.I.E.L.D.'s unique technological innovations. It is an extremely life-like android used to replace people in imminent danger of being killed
First, the supervillain Scorpio stole the technology and used it to create the second team of villains called the Zodiac.
Then some LMDs known as the Deltites achieved sentience and infiltrated S.H.I.E.L.D. and Hydra both, replacing key members until Fury defeated them.
This led to the disbanding of the original organization and its replacement by a new task force with the same acronym under the control of the U.N. ("Strategic Hazard Intervention, Espionage and Logistics Directorate")
The new S.H.I.E.L.D. was meant to be more streamlined so Fury could personally oversee it, but would soon become a large organization again.
In the wake of a disastrous unauthorized mission in Latveria, Fury effectively resigned as executive director, with international warrants out for his arrest.
His first successor was not one of his closer associates but a relatively unknown newcomer to the S.H.I.E.L.D. hierarchy, Maria Hill.

Organizational structure and procedure

The Official Handbook of the Marvel Universe (first edition) describes an eight-level ranking structure (technician, administrator, field agent, regional officer, special officer, regional director, special director, executive director), although providing almost no detail on other aspects of the Directorate's internal makeup.
Years later, the miniseries Agents of Atlas mentioned a position of "sub director," and seemed to indicate that the administrative department of S.H.I.E.L.D. itself referred to simply as "Directorate."

Most of S.H.I.E.L.D.'s agents are normal humans.
The organization attempted to set up a team of superhuman agents, consists of Marvel Man (the future Quasar), Texas Twister, Blue Streak and the Vamp.
But the Corporation, and the team broke apart before it had its first official mission.
A second team organized years later also lasted only a short while.
S.H.I.E.L.D. does employ some superhumans, including in its Psi-Division, composed of telepathic agents who deal with like menaces.
S.H.I.E.L.D. also obtains help from independent heroes when their special abilities are needed.
It has also accepted some superheroes and supervillains as members, but not in a separate unit.
Its headquarters is the Helicarrier, a massive flying aircraft carrier kept airborne at all times and, among other things, containing a squadron of jet fighters and housing an intercontinental ballistic missile (ICBM).
In addition, S.H.I.E.L.D. maintains strong ties to the superhero community, especially Captain America, the Avengers, and the Fantastic Four, and often calls upon that community for aid on particular missions.

Bases of operation
Although the Helicarriers have been considered S.H.I.E.L.D.'s primary mobile home base for a long time, the Directorate also maintains a number of land bases throughout the world, most notably "S.H.I.E.L.D. Central" in New York City.
While some of these land bases are publicly accessible on a limited basis, most of them are not publicly disclosed for reasons of planetary security.
There are also several fully equipped S.H.I.E.L.D. fall-out shelters scattered around the world, while twenty-eight of these shelters only being known to Nick Fury.
During the Civil War, Nick Fury was hiding in an American-based shelter and he also divulged the location of one to Captain America to use it as a safe house