I have very fond memories of Chris, starting way back from my early PhD period around 1980 till the last year, when he spend several months in Würzburg as the Giovanni Prodi Chair in Nonlinear Analysis. The first thing I will never forget was his true enthusiasm and love for mathematics and science that immediately jumped on you when one happened to enter into a scientific conversation with him. Chris was full of other interests as well, and I personally experienced at least as much from him in this direction, too. Before first arriving in Harvard in 1982 (with a backpack, guitar and no single math book), I lived in a rather predictable environment. That short Harvard trip brought me into contact with a lot of new experiences. For example, Chris introduced me to the contemporary American culture of the 1980s and before; an introduction that widened my views quite substantially. Through him I got my love for American folk music like the Grateful Dead. He tried to show me how to play some of their tunes on the guitar (not that easy!) and had so many stories to tell about the group and attached culture! Actually he both played and sang very well. I should also acknowledge some very enjoyable visits to local pubs like The Plough and Stars; regular Chinese lunches at with Chris, Roger and seminar speakers at Harvard Square; happy hours in the evening with visitors from abroad or meeting new friends; dinner parties full of jokes, laughter, good drinks, music and other enjoyments; some private poker sessions at Chris’ home; and so on. These few months in Harvard were certainly one my best and shaped me scientifically and personal. It was Chris, who made all these things happen to me, and I will never forget this.