Dear Arren, It was a real pleasure and privilege to work with you for these few months. When I had to choose the lab for my master's thesis I was captured by your ideas and in fact now I know I couldn't have made a better choice. Under your supervision I learned a lot about metabolic engineering and experienced what is the real life in the lab and how to balance it between with the one outside the lab (I am still pretty far to find an optimal solution though). At every group meeting I was always surprised about how your knowledge was immense and polyedric. You were able to find a solution to nearly every issue "even the corona-related ones" and you always had a smart answer even for the most difficult question. Moreover, when you felt that some basic knowledge was missing by some people in the group you always took your time to do your little lesson on the whiteboard and make things clearer for everyone. I know you did not want to, but I am pretty sure you would have been a great professor. What also was surprising at every meeting was your extravagant personality: you managed always to make us laugh while we were learning. Thanks to you I found my way in science: you made me fall in love with metabolism and metabolic engineering. Now I want to have a career in this field and I know that I will always have you in my heart and in my mind as my first mentor and motivator. I remember bringing to you good news in the Wednesday project meetings: your "very good job Filippo" was the fuel to work even harder and to go home at least at 22 after every meeting "to do things in parallel". I hope I will have great results in my future career under your imaginary supervision and to make some of your ideas become real. The world and the scientific community lost one of its diamonds, you were really smart and years ahead of the other people and who knows what could you have done if your career could last longer, but I am sure that the legacy you left behind will make the world a better place (or at least I can promise that we will try our best). Of course, it was not only about science, your departure left an enormous hole in the hearts of all of us and of all the people that got in contact with you. It was wonderful to share with you this months, I will never stop thanking your for letting me join your family. I wish I told you all this before it was too late, I will live with the regret of not finishing my project in time to see you being proud of me again (and of not attending a Bar-Even Christmas party with you). I like to think that in some way these words will arrive to you and that you will smile reading them. Stay smart and extravagant Arren, wherever you are now. Lots of love, Filippo Federici