The first 1000 days of life constitute an important period for development of health and eating behavior, in particular because the mode of feeding drastically evolves, which involves that the child has to learn “how” to eat, but also “what” to eat, “how” much food to eat. After birth, when foods are orally exposed, infants discover the intrinsic properties of foods, with a variety of tastes, flavors, textures, as well as energy densities. Here we focus on deciphering the involvement of taste and olfaction in the early establishment of eating behavior. In the OPALINE French birth cohort (Observatory of Food Preferences in Infants and Children), taste and flavor preferences were studied in children, in relation with food acceptance over the first two years of life. Both taste and flavor preferences evolve during this period. At the beginning of the complementary feeding period, a higher preference for sweet, sour and umami tastes was associated to a higher acceptance and sweet, sour- and umami-tasting foods, respectively; and similarly, rejection of the odor of trimethylamine and of dimethyl disulphide were related to the rejection of fish and sulphurous cheeses, respectively. Further in development, at 20 mo, food neophobia was associated to flavor differential reactivity (within-subject variability across flavors) but not to taste differential reactivity (within-subject variability across tastes), underlying the importance of olfaction in the development of neophobic reactions. On a longer term, further studies are ongoing to examine the long term effect of taste and flavor exposure on the development of later food preferences.