Since the 1970, savings amounts transferred by migrants to their home countries have constantly increased. They now represent twice the amount of foreign aid and are greater than FDI in developing countries (except BRICs). This article deals with the migrants savings transfers, their determinants, their macroeconomic effects on growth and their microeconomic effects on poverty, inequality and education in the migrants home countries. If no clear conclusion can be drawn on the macroeconomic consequences, microeconomic consequences appear to be truly positive. The migrants decision to return or not to their home countries is also a key factor. But as these transfers induce significant economic issues, they still don't play a major role in the economic policy debates in home countries.