Financing needs for the ecological transition reach trillions of euros and require full mobilization of private markets. To ensure an efficient capital allocation and measure its efficiency in reaching Climate and Nature conservation's targets, Financial institutions need data to appraise the Climate and Biodiversity impacts of their portfolios. That explains the growth of the ESG Data sector since ten years, to support that integration. However, for lack of reporting standards, data quality and availability have been rather problematic. That presentation will stress what is at stake regarding the access to comprehensive, reliable ESG Data, as wrong signals could lead to higher transaction costs, wrong capital allocation decision and greenwashing. It will also describe what is the work of a Fintech specialized in ESG Data, the new jobs (ESG Modellers and Analysts) and carreer paths opened in that sector.