ESA's project FLEX L1B to L2 Retrieval Study officially started on Monday January, 15th (2018), with the Kick-Off meeting. The project aims at developing and optimizing the Level-2 data processing chain for the FLEX/Sentinel-3 tandem mission, ESA's 8th Earth Explorer. Leaded by Magellium (France) with the universities of Valencia (Spain), Milano-Bicocca (Italy) and Bologna (Italy) as members of the consortium, the project will be completed in 24 months and the developed algorithms will serve as baseline for their implementation in the future FLEX Ground Segment. Next project meeting, held in Valencia (Spain), is scheduled for February 13-14 (2018) and will consists on a workshop to discuss about the existing Level-2 data processing chain and future software architecture.