Abstract (IOP)
There are four fundamental extended objects with d>2 world volume dimensions and D-dimensional spacetime supersymmetry: (d=3, D=11), (d=6, D=10), (d=4, D=6) and (d=3, D=4). A simultaneous dimensional reduction of the world-volume and the spacetime then yields four sequences of super-extended object which include the four classical Green-Schwarz superstrings (d=2, D=10, 6, 4 and 3) as special cases. The author discusses which of these models is likely to be quantum consistent and finishes with some speculations.