Abstract: Planet formation can be roughly divided into two stages. In the protoplanetary disk stage, micrometer-sized dust grains coagulate and continue to grow into kilometer-sized planetesimals, followed by planetary embryo formation and run-away gas accretion. After the gaseous disk dispersal in a few million years, hundreds of protoplanets can be formed and they gravitationally interact with each other under the influence of a few giant planets, which leads to many chaotic events such as collisions and ejections. This picture of planet formation is still highly simplified as the whole process is not well understood from both theory (simulations) and observations in many aspects. Because of a 12-order-of-magnitude variation in size from dust grains to planets as well as complex physics at all scales, direct numerical simulations are prohibited and different approaches were developed for studying certain stages of planet formation. From observational point of view, only a tiny portion of the size spectrum is probed by observations. Until recently sub-millimeter-sized dust grains in protoplanetary disks can be well constrained by radial interferometers such as ALMA. On the other hand, matured planetary systems have been discovered by direct and indirect methods (most notably by transit satellite Kepler). In this talk, I will briefly review the current picture of planet formation and recent progress driven by observations. In particular, I will focus on substructures of protoplanetary disks and diversity of extrasolar planetary systems, which can be tested from both the theory and observations.