amino acids, peptides, and proteins offers a noncontact, label-free and nondestructive method of obtaining a better understanding of disease processes both in vitro and in vivo. SHG has further applications in nanoscale characterization, [5] measurement of field-induced carrier motion in photonic devices, [6] and in the development of micro/nanoscale lasers. [7] Qualitative comparison of SHG conversion efficiency suffers from not having a clear benchmark of quantitative values of tensor elements. First principles modeling to obtain quantitative values of the susceptibility tensor such as time-dependent density functional theory is computationally demanding for typical ≥100 atom biomolecule cells and also needs to be benchmarked against experimental values. [8] The β and γ phases of glycine have been recently reported to possess high piezoelectric strain constants. [9] As both the strain and susceptibility tensors of a piezoelectric crystal have an equivalent third rank tensor form, the quantitative susceptibility tensor of glycine crystals provides a useful benchmark for SHG imaging of hierarchical structures in biology that could speed development of quantitative tissue imaging and diseases diagnosis. [10] Glycine is the simplest and only achiral amino acid with a single hydrogen as its side chain, NH 3 + CH 2 COO −. It crystallizes in three distinct phases under ambient conditions α, β, and γ. The carboxyl (COOH) and amino (NH 2) terminal groups become charged to form the zwitterion. [11] The α-phase crystallizes in space group P2 1 /c, comprising of centrosymmetric double layers of zwitterions linked via hydrogen bonds. [12] For this polymorph the presence of a center of symmetry precludes SHG. The β phase shows space group P2 1 and is composed of double layers of zwitterions but the molecular packing is noncentrosymmetric. The γ phase is also SHG active, crystallizing in the noncentrosymmetric trigonal space group P3 1, which forms a 3D molecular network with the zwitterions arranged in helices around the 3 1 screw axis. [13] The difference in properties between phases is due to the differing zwitterion stacking and internal bond angles. [14] Both of the noncentrosymmetric phases of glycine have shown potential as a biocompatible NLO material (Table S1, Supporting Information). A 21 µm thick layer of β glycine nanofibers has been shown to have a larger effective χ (2) relative to 600 µm particles of β glycine due to their subcoherence