Cross section of a computerised model of a crystal of Human Serum Albumin (each side of a square represents one molecule). Images are made by X- raying a crystal of the protein and recording a projection of its electron density. By stacking several such cross-sections together, a low resolution 3-dimensional model of the protein may be built. Knowledge of the molecular structure, including how and where substrates such as minerals and therapeutic drugs bind on, should open the way for pharmaceutical companies to design new drugs or alter existing ones to allow them to be carried more efficiently by the protein molecule through the body.