Legumes

http://www.mayoclinic.com/health/legumes/NU00260
Legumes — a class of vegetables that includes beans, peas and lentils — are among the most versatile and nutritious foods available. Legumes are typically low in fat, contain no cholesterol, and are high in folate, potassium, iron and magnesium. They also contain beneficial fats and soluble and insoluble fiber. A good source of protein, legumes can be a healthy substitute for meat, which has more fat and cholesterol.

http://en.wikipedia.org/wiki/Legume
Nutritional facts
Legumes contain relatively low quantities of the essential amino acid methionine. To compensate, some vegetarian cultures serve legumes along with grains, which are low in the essential amino acid lysine, which legumes contain. Thus a combination of legumes with grains can provide all necessary amino acids for vegetarians. Common examples of such combinations are dal with rice by Indians, and beans with corn tortillas, tofu with rice, and peanut butter with wheat bread (as sandwiches) in several other cultures, including Americans.^[3

http://www.vegetableexpert.co.uk/Legumes.html
Did you know that beans and grain together form a complete protein? Combined, they contain all the amino acids necessary for human health, just like meat or dairy products. The huge Fabaceae, formerly Leguminosae, family (legumes) contains over 16,000 varieties. Common edible legumes include peas, beans, peanuts, lentils, chickpeas, and soybeans.

Gardeners in northern climates are eager to plant peas as soon as the snow melts, as a first rite of spring. Peas are usually the first crop planted in spring gardens.

Further reading:
http://www.mayoclinic.com/health/legumes/NU00260
http://www.healthline.com/galecontent/legumes
http://www.vegetableexpert.co.uk/Legumes.html
http://en.wikipedia.org/wiki/Legume