Co-location of galaxies and the 21cm brightness temperature fields in our illustrative simulation during key stages in the history of the CD and EoR. We show slices at z = 14.8, z = 9.0, and z = 7.0, corresponding to epochs of Lyman alpha coupling, X-ray heating, and reionisation, respectively. Green circles denote 200 galaxies with the brightest UV magnitudes in each slice, with larger circles corresponding to brighter galaxies.