蔡峥，清华大学天文系副教授，天文系副主任。入选国家级青年人才项目。他于2008年毕业于中国科学技术大学，2015年获美国亚利桑那大学理学博士学位，并于2016年获得美国国家航空航天局（NASA）哈勃学者（Hubble Fellow）奖。2019年回国加入清华大学，在高红移星系、星系周气体、大尺度结构等方面取得多个进展，获得第六届腾讯“科学探索奖”，清华大学学术新人奖，良师益友奖，入选2023年度清华大学最受师生关注十大科研进展。此外，他正在领导建设国际最大光谱巡天设备：宽视场巡天望远镜（MUST）。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). Our Keck Cosmic Web Imager and ALMA 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. With both absorption and emission studies, we have identified that the circumgalactic medium (CGM) contains unexpected large quantities of heavy elements. 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 probes, and a potentially new opportunity of a planned 6.5m spectroscopic telescope.