X-ray crystallography was a key element used to draw conclusions about germ line cells and mature antibodies.  In X-ray crystallography, a crystallized molecule is bombarded with a beam of X-rays.  Upon reaching the crystallized structure, the rays diffract according to the electron density of the atoms.  Thus the more dense the electrons, the greater the rays diffract.  This diffraction pattern is then recorded on photographic film.  A scientist must now decipher the diffraction pattern using a computer and a knowledge of proteins, amino acids, and DNA.  Knowing the amino acids that make up certain proteins is essential to deciphering the diffraction pattern because certain amino acids have side chains which help define their shape.   These shapes and holes help give definition to the 3-D structure that scientists form from the diffraction pattern.  Deciphering the diffraction pattern takes several months to several years, but pays off in the end when the final results are obtained.