With the explosive growth of online information, such as news articles, email messages, scientific literature, government documents, and many other kinds of information on the Web, we are overwhelmed with huge amounts of information and have an urgent need for powerful search engines to help manage and make use of all the information. Effectiveness of search engines such as Google directly affects our productivity and life quality. In this talk, I will present an overview of my research on improving search quality and discuss research challenges and opportunities in IR.