Here we describe results which teach us much about the mechanism of the reduction and oxidation of TiO₂(110) by the application of scanning tunnelling microscopy imaging at high temperatures. Titania reduces at high temperature by thermal oxygen loss to leave localized (i.e.  Ti³⁺) and delocalized electrons on the lattice Ti, and a reduced titania interstitial that diffuses into the bulk of the crystal. The interstitial titania can be recalled to the surface by treatment in very low pressures of oxygen, occurring at a significant rate even at 573 K. This re-oxidation occurs by re-growth of titania layers in a Volmer–Weber manner, by a repeating sequence in which in-growth of extra titania within the cross-linked (1 × 2) structure completes the (1 × 1) bulk termination. The next layer then initiates with the nucleation of points and strings which extend to form islands of cross-linked (1 × 2), which once again grow and fill in to reform the (1 × 1). This process continues in a cyclical manner to form many new layers of well-ordered titania. The details of the mechanism and kinetics of the process are considered.