  We present evolutionary calculations for very-low-mass stars and brown dwarfs
based on synthetic spectra and non-grey atmosphere models which include dust
formation and opacity, i.e. objects with $\te\simle 2800$ K. The interior of
the most massive brown dwarfs is shown to develop a conductive core after $\sim
2$ Gyr which slows down their cooling. Comparison is made in optical and
infrared color-magnitude diagrams with recent late-M and L-dwarf observations.
The saturation in optical colors and the very red near-infrared colors of these
objects are well explained by the onset of dust formation in the atmosphere.
Comparison of the faintest presently observed L-dwarfs with these dusty
evolutionary models suggests that dynamical processes such as turbulent
diffusion and gravitational settling are taking place near the photosphere. As
the effective temperature decreases below $\te\approx 1300-1400$ K, the colors
of these objects move to very blue near-infrared colors, a consequence of the
ongoing methane absorption in the infrared. We suggest the possibility ofa
brown dwarf dearth in $J,H,K$ color-magnitude diagrams around this temperature.
