text: There are several techniques used to map out which phase is present during perturbations done on the lipid. These perturbations include pH changes, temperature changes, pressure changes, volume changes, etc.
  The most common technique used to study phospholipid phase presence is phosphorus nuclear magnetic resonance (31P NMR). In this technique, different and unique powder diffraction patterns are observed for lamellar, hexagonal, and isotropic phases. Other techniques that are used and do offer definitive evidence of existence of lamellar and hexagonal phases include freeze-fracture electron microscopy, X-ray diffraction, differential scanning calorimetry (DSC), and deuterium nuclear magnetic resonance (2H NMR).
  Additionally, negative staining transmission electron microscopy has been shown as a useful tool to study lipid bilayer phase behavior and polymorphism into lamellar phase, micellar, unilamellar liposome, and hexagonal aqueous-lipid structures, in aqueous dispersions of membrane lipids. As water-soluble negative stain is excluded from the hydrophobic part (fatty acyl chains) of lipid aggregates, the hydrophilic headgroup portions of the lipid aggregates stain dark and clearly mark the outlines of the lipid aggregates (see figure).