Canned herring is a traditional Swedish food. It is a canned food with bad smell and sour taste. It is made by putting the processed herring into a can and letting it ferment naturally. The biggest feature of fermented herring is its ubiquitous and persistent stench. People who have never eaten pickled herring often cover their noses because of its pungent smell. It is reported that the Swedish government also stipulates that it is not allowed to open canned herring in residential areas. International flights are also not allowed to carry this kind of canned food, because the change of air pressure may lead to the rupture of canned food, with serious consequences. Its smell is 300 times that of natto. It is the most smelly food in the world, and usually comes into the market in Sweden in the short summer (around August). Every year from April to June, when herring lays eggs, fishermen will salvage hundreds of tons of herring to prepare raw materials for curing herring. The uniqueness of pickled herring lies in natural fermentation. In order to ensure that the herring will not rot and deteriorate during fermentation, the producers always put the herring that has just been salvaged into strong salt water and cook it with slow fire, and then put it into a can to let it ferment naturally. It is said that this process of curing herring has been circulating for nearly 300 years. At first, in order to save money, fishermen came up with a method of curing herring by natural fermentation, because it would consume less salt. By mid-August, the herring in the can became sticky and juicy, and the gas in the can also expanded due to the fermentation of the herring, which made the can bulge, which means that the herring has been marinated and can be listed. In Sweden, on the third Thursday of August every year, people hold a party specially for tasting herring, which is said to be the best time to pickle herring. On a warm and short summer night, Swedes set tables and chairs in the garden, and then put herring on the table, enjoying themselves, drinking and singing. People often eat herring with potatoes, onions, sour cream or bland cakes, chew them carefully or swallow them in chunks. Of course, hard liquor is also an essential "throat moistening agent" for people to hold herring parties.