蔡峥，清华大学天文系副教授。2015 年获得美国亚利桑那大学天体物理学博士学位，2015 年—2019 年在美国加州大学圣克鲁兹分校从事博士后研究，获美国太空总署（NASA）“哈勃学者”称号。2019 年任清华大学天文系助理教授，副教授，入选青年人才计划。他发现宇宙早期大尺度结构以及发现宇宙早期最亮的星云。蔡峥领导的多项研究入选哈勃太空望远镜、以及地面最大望远镜的观测计划。他参与多个新望远镜与探测仪器研发，其中，在大型光谱巡天望远镜（MUST）建设中承担关键任务。In this talk, I will present our survey of the massive overdensities and enormous Lya nebulae in the peak of cosmic star formation and QSO activities (z=2--4).  I will present our discovery of a sample of massive overdensies at z~2.3 by utilizing Subaru/HSC, Keck, CFHT and ALMA, selected using the groups of strong Lya absorption. The galaxy properties in these overdensities reflect the emergence of the environmental dependence of galaxy property. I will further discuss the discovery of a large sample of Enormous Lyman alpha nebulae in these extremely overdense fields at high redshift. Our Keck Cosmic Web Imager observations suggest that these nebulae are unique laboratories to study the detailed modeling of how galaxies are fed by the intergalactic medium and circumgalactic medium. In the end, I will talk about the future prospects of how greatly improve our understanding of the structure formation in the next decade with LSST, CMB-S4 and a potentially new opportunity of a planned 6.5m spectroscopic telescope.