Until 15-20 years ago, many nutritionists were mainly interested in the effects of diet on health-related variables such as blood pressure and serum-cholesterol concentrations. Without doubt, these studies have made an important contribution to our current understanding of the relationship between diet and health. For many reasons, however, few researchers. have tried to explain these effects at the molecular level. Nowadays, however, it seems that the picture has been reversed; much research is being directed towards studying the effects of dietary components at the molecular level. This type of research-has been made possible by, among other factors; the implementation of techniques from the more fundamental sciences into nutrition research. Also, the availability of genome sequences has accelerated this shift of interest. The aims of these studies are to obtain detailed information on the molecular and metabolic responses of cells and tissues, or even the whole organism, to dietary components. In these studies, also, the interactions between diet and genetic background, and between diet and different physiological and pathological conditions need to be addressed: However, it is not only important to obtain information on mechanisms, but also on the functional consequences for the organism. One ultimate question, however; is whether this information can be used to develop tests that can form the basis of dietary advice for specific subpopulations. These challenging questions can only be tackled through an integrated approach that combines the expertise from various disciplines.