Glucose metabolism has traditionally been assayed via biochemical means. Fl
uorescence monitoring of NAD(P)H levels has provided a noninvasive method t
o assay glucose metabolism in cells and tissues. However these measurements
have traditionally been of low resolution (no subcellular information) bec
ause of limitations imposed by optical and cellular photodamage problems. T
he recent advent of two-photon excitation microscopy as a dependable tool f
or biological research has opened the possibility of real-time, high-resolu
tion analysis of glucose metabolism in living cells. Such measurements have
the potential to provide subcellular information from intact tissue that c
annot be obtained by other techniques.