Big data refers to the new ability to crunch a vast quantity of information, analyze it instantly, and sometimes draw surprising conclusions from it. As a revolution on par with the internet, big data has changed the way people think about business, health, education, politics, and innovation. In the big-data age, the hypotheses driven approach is no longer efficient to make decisions. Huge dataset and high computing power made sophisticated computational analysis available, especially in correlation analysis. As a consequence big data poses new challenges for statisticians. This presentation introduces the basic characteristics of big data and explores ideas behind it. It also compares statistical methodologies applied in big data and regular clinical trials. Some examples of big data application from CBER/OBE are included.