If you've been reading the news lately, you've probably been reading about Skylon and it being Single Stage To Orbit (SSTO).
I've had a think back and to the best of my knowledge humanity has always used multi-stage rockets. Am I wrong? Has humanity ever launched to Earth orbit carrying the initial stage?
I'm not sure what the technical definition of a "stage" is but I take it to mean jettisoning anything other than propellant - so engines, tanks, etc.