Recent experiments and computer simulations show that supercooled liquids around the glass transition temperature are "dynamically heterogeneous" [1]. Such heterogeneity is expected from the random first order transition theory of the glass transition. Using a microscopic approach based on this theory, we derive a relation between the departure from Debye relaxation as characterized by the β value of a stretched exponential response function ϕ(t) =e^-(t/ τ_KWW)^β, and the fragility of the

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... . The β value is also predicted to depend on temperature and to vanish as the ideal glass transition is approached at the Kauzmann temperature.