Drying, or desiccation, is known to preserve biomaterials, including foods. In freeze-drying, water is evaporated in a frozen state in a vacuum, by means of sublimation (the process of changing a solid to a vapor without first changing it to a liquid). In 1811, John Leslie had first caused freezing by means of the evaporation and sublimation of ice. In 1813, William Wollaston demonstrated this process to the Royal Society of London. It does not seem to have occurred to either Leslie or Wollaston to use sublimation for drying. That distinction goes to Richard Altmann, a German histologist, who dried pieces of frozen tissue in 1890. Later, in 1903, Vansteenberghe freeze-dried the rabies virus. In 1906, Jacques Arsene d’Arsonval removed water at a low temperature for distillation. Since water removal is the essence of drying, d’Arsonval is often credited with the discovery of freeze-drying, but the first clearly recorded use of sublimation for preservation was by Leon Shackell in 1909. His work was widely recognized, and he freeze-dried a variety of biological materials. The first patent for freeze-drying was issued to Henri Tival, a French inventor, in 1927. In 1934, William Elser received patents for a modern freeze-drying apparatus that supplied heat for sublimation. In 1933, Earl W. Flosdorf had freeze-dried human blood serum and plasma for clinical use. The subsequent efforts of Flosdorf led to commercial freeze-drying applications in the United States. With the freeze-drying technique fairly well established for biological products, it was a natural extension for Flosdorf to apply the technique to the drying of foods. As early as 1935, Flosdorf experimented with the freeze-drying of fruit juices and milk. An early British patent was issued to Franklin Kidd, a British inventor, in 1941 for the freeze-drying of foods. An experimental program on the freeze-drying of food was also initiated at the Low Temperature Research Station at Cambridge University in England, but until World War II, freeze-drying was only an occasionally used scientific tool. It was the desiccation of blood plasma from the frozen state, performed by the American Red Cross for the U.S. armed forces, that provided the first spectacular, extensive use of freeze-drying. This work demonstrated the vast potential of freeze-drying for commercial applications. In 1949, Flosdorf published the first topic on freeze-drying, which laid the foundation for freeze-drying of foods and remains one of the most important contributions to large-scale operations in the field. In the topic, Flosdorf described the freeze-drying of fruit juices, milk, meats, oysters, clams, fish fillets, coffee and tea extracts, fruits, vegetables, and other products. Flosdorf also devoted an entire topic to describing the equipment used for both batch and continuous processing, and he discussed cost analysis. The holder of more than fifteen patents covering various aspects of freeze-drying, Flosdorf dominated the move toward commercialization in the United States. Flosdorf’s vision and ingenuity in applying freeze-drying to foods has revolutionized food preservation. He was also responsible for making a laboratory technique a tremendous commercial success. Freeze-drying is important because it stops the growth of microorganisms, inhibits deleterious chemical reactions, and facilitates distribution and storage. Freeze-dried foods are easily prepared for consumption by adding water (rehydration). When freeze-dried properly, most foods, either raw or cooked, can be rehydrated quickly to yield products that are equal in quality to their frozen counterparts. Freeze-dried products retain most of their nutritive qualities and have a long storage life, even at room temperature. Freeze-drying is not, however, without disadvantages. The major disadvantage is the high cost of processing. Thus, to this day, the great potential of freeze-drying has not been fully realized. The drying of cell-free materials, such as coffee and tea extracts, has been extremely successful, but the obstacles imposed by the cell membranes in foods such as fruits, vegetables, and meats have limited the application to expensive specialty items such as freeze-dried soups and to foods for armies, campers, and astronauts. Future economic changes may create a situation in which the high cost of freeze-drying is more than offset by the cost of transportation and storage.