The Elfe children are now three and a half years old , and a new survey was launched on 21 October to gather more detailed information about early childhood. This survey was conducted for the first time by telephone and through home visits with the families. The success of this new stage comes from the investment made by all of the families who believe in the value of this research, which will continue until their child turns 20 years old. Led by INED and INSERM, and in partnership with EFS, this study requires many stages starting from data collection up until the researchers publish the results. Some of this data has just been published in the three fields of health, environment and social sciences.