Arren was a very special person and working with and next to him was an experience I will always keep in good memory. While he was loud, annoying and grumpy, he was at the same time also a brilliant mind (not only in science), a great mentor you could always approach with any kind of question or idea, and simply the most honest person I have ever met. He would always find time to help, even in his most busy moments. I always had the feeling that he really cared for his group and that he wanted to make sure that we are all getting somewhere – not only scientific but also on a personal level. I will miss him. Rest in peace, Arren. Fabian