The importance of nutrition in early childhood has been widely demonstrated in terms of its association with morbidity, both in the short and long term. From birth, the period of exclusive breastfeeding, followed by the introduction of other foods to achieve a diet diversified to meet the nutritional needs of young children, appears to be linked to the risk of infections, allergies, and certain chronic diseases such as diabetes. The benefit of breastfeeding for the prevention of breast cancer in mothers was also highlighted in the 2007 report of the World Cancer Research Fund (WCRF). In France, recommendations have been issued by the High Authority for Health and as part of the National Nutrition and Health Program (PNNS). Data from the National Perinatal Survey (ENP) show that breastfeeding is currently practiced with insufficient frequency in France. In 2003, nearly two-thirds of women had initiated breastfeeding in the maternity ward, with significant geographic and social disparities. Just over half were exclusively breastfeeding. Since the ENP covers only the first few days of a child’s life, these rates can be considered very low. Furthermore, no information on the duration of breastfeeding, the degree of exclusivity, or the age at which complementary feeding begins is currently available at the national level. A study conducted for the French Union of Infant Foods, every 8 years since the 1980s, focuses on the use of infant formula and the introduction of complementary foods. However, it has significant methodological limitations (recruitment excluding any breastfed children, sample size, data collection) and its results center on the use of commercially available foods. Nevertheless, the weaning period (child’s age, order of introduction, and type of foods) is equally important in terms of meeting nutritional needs and its implications for children’s long-term health. The need for public health assessment, combined with the lack of relevant data, led us to conclude that monitoring the diets of children under 1 year of age should be a priority. The cohort of the French Longitudinal Study from Childhood (ELFE) cannot meet this objective because a tool is needed that allows for the regular repetition of such data collection to measure changes in practices in line with current recommendations. The Unit for Nutritional Surveillance and Epidemiology (USEN), a joint unit of the French Institute for Public Health Surveillance and the University of Paris 13, was tasked with conducting the Épifane study in 2012–2013, which, due to its national scope, simplicity, and reproducibility, should meet this need. (R.A.)