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5.1 Introduction
Advances in imaging technologies drive a constant progress in our capability of probing structures and
their dynamics within cells and tissues. e application of nonlinear spectroscopy to optical micros-
copy (Denk etal., 1990; Helmchen and Denk, 2005; Zipfel etal., 2003b) has led to new perspectives both
in basic research and in the potential development of very powerful noninvasive diagnostic tools. Some
of these techniques permit optical probing of biological functions (Dombeck etal., 2004; Skala etal.,
2007; Svoboda and Yasuda, 2006; Zipfel etal., 2003a), as well as monitoring molecular structure and
dynamics in ...