  Magneto-convection simulations with two scenarios have been performed: In
one, horizontal magnetic field is advected into the computational domain by
fluid entering at the bottom. In the other, an initially uniform vertical
magnetic field is imposed on a snapshot of non-magnetic convection and allowed
to evolve. In both cases, the field is swept into the intergranular lanes and
the boundaries of the underlying mesogranules. The largest field concentrations
at the surface reach pressure balance with the surrounding gas. They suppress
both horizontal and vertical flows, which reduces the heat transport. They
cool, become evacuated and their optical depth unity surface is depressed by
several hundred kilometers. Micropores form, typically where a small granule
disappears and surrounding flux tubes squeeze into its previous location.
