Convection in the Sun is apparently cellular and the convective velocities can be estimated. The interaction of cellular convection with a weak magnetic field leads to concentrated ropes of flux in the convective zone with fields of about 5000 gauss and fluxes of 10 21 maxwells in agreement with observation. These flux tubes tend to float outwards from the centre of the Sun. The magnetic pressure associated with the fields required to halt photospheric convection is comparable with the gas pressure and so fields will generally be diffuse as in bipolar magnetic regions. Occasionally the flux is concentrated to form a sunspot but the cooling is insignificant at more than 1000 km below the surface of the Sun.