Originally Posted by Spats
I forgot you weren't a native English speaker -- my first impulse was "Great, another little emo kid who thinks emo started in the late 1990s." Sorry for being harsh.
I think we can split "emo" into two main waves:
1) Punk emo, which started with Husker Du around 1982 and moved on through Rites of Spring, Dag Nasty, Fugazi, Jawbox, and so on.
2) Post-punk emo, which started with Slint's "Spiderland" in 1991 and moved on through all the other bands (SDRE, Texas Is The Reason, etc.)
I consider pop emo (Green Day, Weezer) an outgrowth of punk emo.