The complexity of the conditions of life in the 20th century may be well illustrated from the grain trade of the world. The ordinary bread sold in Great Britain represents, for example, produce of nearly every country in the world outside the tropics.

The grain trade refers to the local and international trade in cereals and other food grains such as wheat, barley, maize, and rice. Grain is an important trade item because it is easily stored and transported with limited spoilage, unlike other agricultural products. Healthy grain supply and trade is important to many societies, providing a caloric base for most food systems as well as important role in animal feed for animal agriculture.

The grain trade is as old as agricultural settlement, identified in many of the early cultures that adopted sedentary farming. Major societal changes have been directly connected to the grain trade, such as the fall of the Roman Empire. From the early modern period onward, grain trade has been an important part of colonial expansion and international power dynamics. The geopolitical dominance of countries like Australia, the United States, Canada and the Soviet Union during the 20th century was connected with their status as grain surplus countries.

More recently, international commodity markets have been an important part of the dynamics of food systems and grain pricing. Speculation, as well as other compounding production and supply factors leading up to the 2007-2008 financial crises, created rapid inflation of grain prices during the 2007–2008 world food price crisis. More recently, the dominance of Ukraine and Russia in grain markets such as wheat meant that the Russian invasion of Ukraine in 2022 caused increased fears of a global food crises in 2022. Changes to agriculture caused by climate change are expected to have cascading effects on global grain markets.