Spin the top and it will invert itself whilst spinning! It does this because its centre of mass does not coincide with the geometrical centre of the sphere. This means that when spinning the bulbous top slides over the surface on which it is spinning and this friction and motion causes enough force to ‘drive’ the spinning top up and over until it is spinning on the stalk. Once on the stalk, there are far less sliding forces and the top can now spin stably until it no longer has enough energy to sustain its speed and spin.