A method of multiphoton photosensitizing a photoreactive composition
comprises irradiating the composition with light sufficient to cause
simultaneous absorption of at least two photons, thereby inducing at least
one acid- or radical-initiated chemical reaction where the composition is
exposed to the light. The composition comprises: (a) at least one reactive
species that is capable of undergoing such reaction; and (b) at least one
multi-component, multiphoton photoinitiator system.
