 It had a structure at the time that was almost completely unknown, and when Hodgkin discovered it contained cobalt, she realized the structure actualization could be determined by x-ray crystallography analysis.The large size of the molecule, and the fact that the atoms were largely unaccounted for—aside from cobalt—posed a challenge in structure analysis that had not been previously explored.From these crystals, she deduced the presence of a ring structure because the crystals were pleochroic, a finding which she later confirmed using X-ray crystallography.