Several days have passed, I still can not believe the reality. I met Professor Li several times in different conferences and workshops. I remember clearly he had always been very kind and willing to talk to young students & junior researchers and introduce us to each other. Just two weeks ago in the IMA workshop, I asked him for some advice after one day's session. He said: "This is your first visit to the University, right? Let's take a walk while talking. I will show you some places of interests in the campus". During the walk, he gave me many useful advice and tips in research and also showed the university center, the shoe tree, the river and the trail he used to mountain biking last summer... These days, those pictures flashed back many times in my mind like just happened yesterday. I think those pictures are also a wonderful highlight of Professor Li to me: An interesting, considerate, enthusiastic mathematician who is always with full love and curiosity to life and new challenges. R.I.P. Professor Li. I miss you. My deepest condolences to your family.