  Using the initial peculiar velocity field, we analytically study the
hierarchical formation of gravitationally bound objects. The field is smoothed
over a scale that corresponds to the mass of a given class of objects. Through
the Zel'dovich approximation, the smoothed field determines how the objects
cluster together to form a new class of more massive objects. The standard
cosmological parameters lead to the evolution of primordial clouds with 10^6
M(sun) -> galaxies with 10^12 M(sun) -> clusters of galaxies with 10^15 M(sun)
-> superclusters of galaxies with 10^16 M(sun). The epochs obtained for the
formation of these classes of objects are consistent with observations.
