  An analysis of a tower of hidden sectors coupled to each other, with one of
these hidden sectors coupled to the visible sector, is given and the
implications of such couplings on physics in the visible sector are
investigated. Thus the analysis considers $n$ number of hidden sectors where
the visible sector couples only to hidden sector 1, while the latter couples
also to hidden sector 2, and the hidden sector 2 couples to hidden sector 3 and
so on. A set of successively feeble couplings of the hidden sectors to the
visible sector are generated in such a set up. In general each of these sectors
live in a different heat bath. We develop a closed form set of coupled
Boltzmann equations for the correlated evolution of the temperatures and number
densities of each of the heat baths. We then apply the formalism to a
simplified model with scalar portals between the different sectors. Predictions
related to dark matter direct detection experiments and future CMB probes of
dark radiation are made.
