Abstract
The past hundred years marked the golden era of cosmic explorations. Our knowledge about the universe has reached an unprecedented depth attributing to the theoretical and observational developments. Meanwhile new challenges emerge leading to the continued excitement in probing cosmic mysteries. Because of the statistical nature, large astronomical surveys become increasingly important in cosmological studies. They can provide massive data to shed light on our understanding about the cosmos. In this article, we will discuss the knowns and unknowns about the universe from past and current studies. Expectations from next generation of large surveys and the challenges therein will also be presented.