Abstract: With the successful commissioning of the James Webb Space Telescope (JWST), JWST has produced a revolution in using photometric redshifts and/or multi-colour selection criteria to find galaxies at the extreme redshifts. These discoveries offer a unique opportunity to answer questions regarding the formation of galaxies in the early Universe. In this talk, I’ll present our latest discovery of mergers during the Epoch of Reionization (EoR) using JWST. We'll discuss these galaxies' properties and characteristics, such as their stellar mass history, star formation activities, and interstellar medium properties. Furthermore, I will show how we employ NIRCam deep imaging data for a quantitative study of the galaxy environment. It is the first systematic investigation of high-redshift mergers and their evolution with redshift at z>5. On a larger scale, I will introduce the study of high-redshift clustering in the CEERS field, mapping the Universe's dense regions on the Mpc scale. We have also quantitatively identified potential protocluster candidates. Notably, AGNs consistently coexist with dense galaxy environments. I will also show how the combination of NIRCam and deep MIRI photometry offers a reliable method for AGN identification.
