For more than two decades, space-based estimates of phytoplankton distributions in oceans have been possible using chlorophyll fluorescence. The possibility of land-based solar-induced chlorophyll fluorescence (SIF) retrievals for ecosystems was first formally proposed in 2005 as one of seven ESA Earth Explorer 7 mission concepts, the Fluorescence EXplorer (FLEX). However, the EE7 winner after the January 2009 community User Consultation Meeting (UCM) was BIOMASS. Subsequently, the FLEX concept was slimmed down and supported as one of two pre-Phase A EE8 mission concepts, along with CarbonSat, beginning in 2011. Betsy was recruited by ESA to serve (2006-2009) on the FLEX EE7 Mission Advisory Group (MAG), and again for the EE8 MAG (2011-2015). This time FLEX prevailed as the unanimous choice of the ESA review panel and the general science community attending the recent UCM in Krakow, Poland. During the past 3 years, paralleling this second FLEX concept development, space-based observations of chlorophyll fluorescence of terrestrial vegetation from coarse spatial resolution atmospheric chemistry satellites have become all the rage, supporting the importance and potential of FLEX as a true Earth Explorer of the biosphere.