  For the description of the early inflation, and acceleration expansion of the
Universe, compatible with observational data, the 5D noncompact Kaluza--Klein
cosmology is investigated. It is proposed that the 5D space is filled with a
null perfect fluid, resulting a perfect fluid in 4D universe, plus one along
the fifth dimension. By analyzing the reduced field equations for flat FRW
model, we show the early inflationary behavior and current acceleration of the
universe.
