Cheng Li is a Professor at Department of Astronomy, Tsinghua University. Before he joined Tsinghua in September 2015, he worked at Shanghai Astronomical Observatory as a group leader (2010-2015) and Max-Planck Institute for Astrophysics as a postdoc (2007-2010). He obtained his PhD from USTC in 2006. His research has been focused on the structure, formation and evolution of galaxies, as well as the large-scale structure of the Universe. He is a member of the SDSS-IV and Subaru/PFS projects.Galaxy Astronomy began in Oct 1923 when Edwin Hubble observed a Cepheid variable star in the Andromeda Nebula to be more than 2 million light years away. After a century of studies, our understanding of both our Milky Way galaxy and external galaxies has dramatically advanced thanks to the development of Cosmology, high performance computing and large observational facilities. There are still many fundamental but open questions in galaxy formation and evolution, however. I will briefly review the current questions and attempt to answer some of them based on our recent work on optical spectroscopic and multiband imaging surveys of galaxies. In particular I will talk about the formation histories of dwarf and massive galaxies, the resolved stellar populations, dust, gas and star formation histories within nearby galaxies, and the cold and warm gas content of galaxies and their dark matter halos, etc.