The ALMA revolution of planet formation: structures of gas and dust in planet-forming disksProtoplanetary disks of gas and dust around young stars are the birth cradles of planets. The study of these disks was for a long time based on unresolved observations, limiting our understanding of planet formation. Of particular interest are the so-called transitional disks with inner dust cavities, a sign of active evolution. The arrival of ALMA has revolutionized our view of the structure of these disks. ALMA observations in the last few years have revealed rings, asymmetries, dust/gas segregation, gas dynamics, evidence for dust trapping and vortices, and many more exciting phenomena that have been predicted for decades in disk models. Using new physical-chemical modeling tools it is now possible to constrain gas and dust densities and compare these with planet-disk interaction model predictions. In this talk I will discuss several recent ALMA discoveries and the next steps in planet formation studies.