S.H.I.E.L.D.

S.H.I.E.L.D. is a fictional espionage, law enforcement, and counter-terrorism agency. They appeared in American comic books published by Marvel Comics. It was created by Stan Lee and Jack Kirby in "Strange Tales" #135 (Aug. 1965).
Missions.
It often deals with superhuman threats to international security.
Naming.
The acronym was for Supreme Headquarters, International Espionage and Law-Enforcement Division. It was changed in 1991 to Strategic Hazard Intervention Espionage Logistics Directorate. Within the various movies set in the Marvel Cinematic Universe, as well as many animated and live-action television series, the backronym stands for Strategic Homeland Intervention, Enforcement and Logistics Division.
In media.
The organization has appeared in media adaptations as well as movies and shows that take place in the Marvel Cinematic Universe.