  We present a general description of the scalar field dark matter (SFDM)
hypothesis in the cosmological context. The scenario of structure formation
under such a hypothesis is based on Jeans instabilities of fluctuations of the
scalar field. It is shown that it is possible to form stable long lived objects
consisting of a wide range of typical galactic masses around $10^{12}M_{\odot}$
once the parameters of the effective theory are fixed with the cosmological
constraints. The energy density at the origin of such an object is smooth as it
should.
