The FB Study has advanced approaches for retrieval & applications of solar-induced fluorescence (SIF) for assessment of photosynthesis & stress status in terrestrial vegetation, including development of a calibration/validation strategy for FLEX products.  Specific advances include:  (i) optimisation of SIF retrieval algorithms, formalisation of fluorescence-derived indices, and development of biophysical products;  (ii) SIF-photosynthesis model improvements and evaluation of data assimilation techniques;  (iii) testing of stress indices, extension of the range of potential applications, and evaluation of non-photochemical protection mechanisms;  and (iv) development of calibration/validation strategies, including metrics for validation error & product accuracies, definition of FLEX Level 2/3 products and their validation plan, and definition of a common protocol and state-of-the-art instruments to be used for estimation of fluorescence in the context of cal/val activities.  This activity now forms the foundation for subsequent science & applications development during FLEX mission development & deployment.