  Cold atoms in optical lattices are described in {\it real space} by
multi-orbital mean-field Ans\"atze. In this work we consider four typical
systems: (i) spinless identical bosons, (ii) spinor identical bosons (iii),
Bose-Bose mixtures, and (iv) Bose-Fermi mixtures and derive in each case the
corresponding multi-orbital mean-field energy-functional and working equations.
The notions of {\it dressed} Wannier functions and Wannier spinors are
introduced and the equations defining them are presented and discussed. The
dressed Wannier functions are the set of orthogonal, translationally-equivalent
orbitals which minimizes the energy of the Hamiltonian including boson-boson
(particle-particle) interactions. Illustrative examples of dressed Wannier
functions are provided for spinless bosonic atoms and mixtures in
one-dimensional optical lattices.

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