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11.1 Introduction
e biological molecules that exhibit second-harmonic generation (SHG) include brillar collagens,
myosin, microtubules, silk, and cellulose [1–4]. Laser scanning microscopy (LSM) allows for nonin-
vasive and nondestructive three-dimensional imaging of the SHG signal from biological samples pos-
sessing second-harmonic-generating molecules [5–9]. As an optical signal, SHG is uniquely sensitive to
the spatial organization of generating dipoles [10–14], allowing for quantitative and selective structural
characterization of second-harmonic-generating tissue. Numerous optical and structural parameters
have been derived from ...