During the last decades, our understanding on both galaxy and structure formation in the nearby Universe has been great advanced, thanks to various large cosmological surveys. On the other hand, limited by the capabilities of current facilities, the early stages of both galaxy and structure formation are still not well understood. On a theoretical view, many physical properties of high-redshift galaxies and structures are still difficult to reproduced in current models/simulations. In this talk, I will first introduce some of the main challenges we are facing currently regarding massive galaxy and structure formation at high redshifts, and then present our recent observational results that provide new insights into these issues. In particular, I will show how we discovered a new and dominant population of massive galaxies in the early universe that have been completely missed in previous surveys. In addition, I will present how we discovered the most distant, and also a novel type of galaxy clusters at high redshifts. Their indications on high-redshift galaxy and cluster formation will be discussed.