Qingyun, Five years has passed since we first fell in love. I still remember the first time you asked me for a date. You came to see my performance as part of the PKU ballroom dancing team, and waited for an hour after the performance, while we were cleaning up the venue, only to ask me to go out for some late night food. We are each other's first love. This sounds romantic, but also means we are both inexperienced in maintaining a loving relationship. What makes things more interesting is that we are very different people. It's great that we are understanding and adapting to each other. I feel lucky to have you as my life partner. You are adventurous and outgoing, like a rainbow that colored my life. You dragged me away from the computer, and traveled to Hawaii, Alaska, Yellow Stone, New York.... You encouraged me to learn skiing and surfing, which I would not dare to try on myself. You have a wide circle of friends, and I get to know many interesting person because of you. I'm even more grateful that you are cheerful and optimistic, like warm sunshine in my doomy days, giving me comfort and support through the many frustrations and despair. Time has tested our relationship. Hand in hand we have walked through the challenging years of a Ph.D. More challenges await as we start our career, and take more responsibilities to our families. I believe we can compliment each other and make a good team.I want to live the rest of my life with you. I love you.