  This paper reports the results of the numerical study of the formation of
aspherical Planetary Nebulae through the Generalised Interacting Winds Model,
taking into account the effects caused by the evolving central star and fast
wind. The results show for the first time that aspherical nebulae do form
within the required time scale. Consideration of the development of the nebula
shows that in the early stages it is the ionization of the aspherical AGB wind
that contributes considerably to the shaping of the nebula. Furthermore the
passing through of the ionization front may modifies the density distribution
in the slow wind, leading to the formation of a surrounding envelope, and
sometimes a different morphology for the nebula than was to be expected from
the initial conditions. I consider how the different phases of ionization
fronts and wind swept bubbles can be observationally distinguished.
