  The ionisation structure of the Intergalactic Medium (IGM) during
reionisation is sensitive to the unknown galaxy formation physics that
prevailed at that time. This structure introduces non-Gaussian statistics into
the redshifted 21 cm fluctuation amplitudes that can only be studied through
tomographic imaging, which will clearly discriminate between different galaxy
formation scenarios. Imaging the ionisation structure and cosmological HII
regions during reionisation is therefore a key goal for the SKA. For example,
the SKA1-LOW baseline design with a 1 km diameter core will resolve HII regions
expected from galaxy formation models which include strong feedback on low-mass
galaxy formation. Imaging the smaller HII regions that result from galaxy
formation in the absence of SNe feedback will also be possible for SKA1-LOW in
the later stages of reionisation, but may require the greater sensitivity of
SKA early in the reionisation era. In addition to having baselines long enough
to resolve the HII regions, the field of view for SKA1-LOW reionisation
experiments should be at least several degrees in order to image the largest HI
structures towards the end of reionisation. The baseline design with 35 meter
diameter stations has a field of view within a single primary pointing which is
sufficient for this purpose.
