Sierk van Terwisga is a PSF fellow working on the evolution of protoplanetary disks from an observational perspective, and particularly, on how they are affected by their environment. The sensitivity and speed of ALMA make it possible to study these effects, which are difficult to identify in individual disks, by observing large populations of disks in different environments and at different ages. His research combines observations of both the dust and molecular gas in these systems to get new constraints on how planet formation proceeds.