Eggs are difficult to dry, and it was not until the early 20th century that a workable process was developed, by German engineers in China. From the 1930s onwards other countries, including the USA and Britain, began to dry eggs, for baking and other processed foods. During the Second World War dried egg was used in Britain and elsewhere, for different and obvious reasons, but domestic use of the product has since almost ceased, although its quality has improved. Eggs may be dried whole, or separated into yolks and whites.