Structure and Interactions of Lipid Bilayers: Role of Fluctuations NagleJohn F. Tristram-NagleStephanie 2001 <p>The cell is the fundamental unit in biology. Each cell is spatially defined by its cytoplasmic membrane. The structural basis for each membrane is lipid in bilayer form. Following this reductionist point of view, it is therefore not surprising that lipid bilayers have been much studied using a great variety of techniques.</p>