XML
Extensible Markup Language
From Charles Goldfarb's website...
Ed Mosher, Ray Lorie, and I invented the first structured markup language in 1969, IBM's "Generalized Markup Language" (GML). In 1970 I coined the phrase "markup language" in order to describe our invention.
GML led to SGML, which I invented in 1974. SGML literally makes the infrastructure of modern society possible. Our incredibly complex systems and products require massive amounts of documentation -- 4 million pages for a single model of aircraft, for example, which must be updated quarterly. That documentation couldn't be created and managed without SGML.
The same is true for the documentation of nuclear plants, oil rigs, government laws and regulations, military systems -- and anything else that is too complex for a single person to understand and that has life-and-death significance. All of those things are documented with SGML.