Insulin is a therapeutic protein that is used to treat diabetes. For better patient care, insulin preparations that are either long-acting (basal insulin) or fast-acting (meal insulin) are required. Crystals and crystallography play a major role in research of new insulin preparations partly because some long-acting preparations are suspensions of micro-crystals, and partly because crystals of insulin molecules can be used for the detection of their 3 Dimensional structure, which then is the basis for a targeted structure-based design. The lecture will provide a brief history of various insulin products seen from a crystallographic point of view.