Ideal food should be delicious and nutritious.But sometimes,the food you eat is delicious but not nutritious,or nutritious but not delicious.To let animals know which to be delicious or nutritious is an important or valuable question.In a recent article published in Nature Neuroscience[1],Friedman JM et al addressed this question and showed that the level of hormone leptin and dopamine system co-regulated the reward value of food in mice.