Plants can provide most of the nutrients for the human diet. However, the major crops are often deficient in some of the nutrients. Thus, malnutrition, with respect to micronutrients such as vitamin A, iron, and zinc, but also macronutrients such as the essential amino acids lysine and methionine, affects more than 40% of the world's population. Recent advances in molecular biology, but also the grasp of biochemical pathways, metabolic fluxes, and networks can now be exploited to produce crops enhanced in key nutrients to increase the nutritional value of plant-derived foods and feeds. Some of the predictions appear to be accurate, while others not, reflecting the fact that plant metabolism is more complex than presently understood. A good example for a complex regulation is the methionine biosynthetic pathway in plants. The nutritional importance of Met and cysteine has motivated extensive studies of their roles in plant molecular physiology, especially regarding to their transport, synthesis, and accumulation in plants. Recent studies have demonstrated that Met metabolism is regulated differently in various plant species.