MRI is the only technique that has the potential to map the temperature distribution of water in food non-invasively in three dimensions (Nott and Hall, 1999), as well as to acquire data sensitive to the physical changes induced by heating, including delineating between frozen and thawed regions. Its practical use is illustrated here by the following set of applications: microwave heating of plastic trays containing a model gel, as well as chilled and frozen lasagne; thawing of a frozen whole chicken either at ambient temperature or by microwave heating; and by cooking of an egg in hot water. The strengths and limitations of MRI temperature mapping of real foods is discussed.