  We introduce a very early universe model based on the thermodynamics of a gas
of closed strings in a background which is non-perturbative in $\alpha'$. Upon
considering the fully $\alpha'$-corrected equations extended to include certain
anisotropic cosmological backgrounds, we describe the evolution of the system
in three different stages parametrized by the gas' equation of state. Using
standard string thermodynamical arguments, we start with an isotropic
10-dimensional universe inside the string scale and evolve it towards a
universe with four large spacetime dimensions and six stabilized internal
dimensions in the Einstein frame.
