A Brief “History” of String Theory
Here is a very brief “history” of the development of string theory. These details are destined to fill many large volumes written by many people directly and indirectly involved in this research.
Some believe that string theory helps to explain the “Shadow” people.
Others, the existence of the one true “God” of all the universe…
Read on….
1921 
KaluzaKlein Theory 

Electromagnetism can be derived from gravity in a unified theory if there are four space dimensions instead of three, and the fourth is curled into a tiny circle. Kaluza and Klein made this discovery independently of each other. 
1970 
String Theory is Born 

Three particle theorists independently realize that the dual theories developed in 1968 to describe the particle spectrum also describe the quantum mechanics of oscillating strings. This marks the official birth of string theory. 
1971 
Supersymmetry 

Supersymmetry is invented in two contexts at once: in ordinary particle field theory and as a consequence of introducing fermions into string theory. It holds the promise of resolving many problems in particle theory, but requires equal numbers of fermions and bosons, so it cannot be an exact symmetry of Nature. 
1974 
Gravitons 

String theory using closed strings fails to describe hadronic physics because the spin 2 excitation has zero mass. Oops, that makes it an ideal candidate for the missing theory of quantum gravity!! This marks the advent of string theory as a proposed unified theory of all four observed forces in Nature. 
1976 
Supergravity 

Supersymmetry is added to gravity, making supergravity. This progress is especially important to string theory, where gravity can’t be separated from the spectrum of excitations. 
1980 
Superstrings 

String theory plus supersymmetry yields an excitation spectrum that has equal numbers of fermions and bosons, showing that string theory can be made totally supersymmetric. The resulting objects are called superstrings. 
1984 
The Big Year For String Theory! 

This was the year for string theory! Deadly anomalies that threatened to make the theory senseless were discovered to cancel each other when the underlying symmetries in the theory belong two special groups. Finally string theory is accepted by the mainstream physics community as an actual candidate theory uniting quantum mechanics, particle physics and gravity. 
1991 
The Duality Revolution 

Interesting work on stringy black holes in higher dimensions leads to a revolution in understanding how different versions of string theory are related through duality transformations. This unlocks a surge of progress towards a deeper nonperturbative picture of string theory. 
1996 
Black Hole Entropy 

Using Einstein relativity and Hawking radiation, there were hints in the past that black holes have thermodynamic properties that need to be understood microscopically. A microscopic origin for black hole thermodynamics is finally achieved in string theory. String theory sheds amazing light on the entire perplexing subject of black hole quantum mechanics. 
For more information, and updated research items, visit wikipedia here.