I met Arren in 2011 when we invited him to present at the Gordon Research Conference on CO2 Assimilation (https://www.grc.org/co2-assimilation-in-plants-genome-to-biome-conference/2011/). I was a Vice-Chair for that conference and the discussion leader for the early career/hot off the press talks where he presented "The design and analysis of synthetic carbon fixation pathways". It was fascinating and ambitious, and our discussions during the rest of the meeting were intense and great. I wasn't sure it would work, but I really found his approach interesting and inspiring. I have been following his work ever since, mentioning it in my classes at least once per year. It is very sad that he is gone from our community, but it is clear that he has left a legacy that will endure. -David Hanson, University of New Mexico, USA.