Carbohydrates come in two forms - there are simple and complex carbohydrates. Simple carbohydrates are up to three units of sugar linked together with a single molecule. Complex carbohydrates are hundreds of sugar units linked together with a single molecule. Simple sugards can be easily identified because they taste sweet. Complex carbohydrates are pleasant, but not sweet. Most carbohydrates come from cereals and grains, and much of them in today's diet can be found in bread and potatoes. The body converts them into energy in a complicated process, and the body has a basic requirement for carbohydrates.