  We use Chiral Perturbation Theory to compute the nucleon mass-shift due to
finite volume and temperature effects. Our results are valid up to
next-to-leading order in the "\eps-regime" (mL ~ m\beta << 1) as well as in the
"p-regime" (mL ~ m\beta >> 1). Based on the two leading orders, we discuss the
convergence of the expansion as a function of the lattice size and quark
masses. This result can be used to extrapolate lattice results obtained from
lattice sizes smaller than the pion cloud, avoiding the numerical simulation of
physics under theoretical control. An extraction of the low-energy coefficient
c_3 of the chiral Lagrangean from lattice simulations at small volumes and a
``magic'' ratio \beta=1.22262 L might be possible.
