Example reconstruction of a 2D reionisation time map from a 2D map of the 21 cm signal taken at a redshift of z = 11. The left and middle panels are the brightness temperature and reionisation time fields generated by a 21cmFAST simulation. The right panel is the reconstruction of the reionisation times with the neural network designed to reproduce the true reionisation time map of the middle panel. Both t_reion(r) maps are dimensionless.