Extrasolar planets are now known to be ubiquitous and highly diverse, which implies that planet formation must be a robust and efficient process. Protoplanetary disks are the sites of ongoing planet formation in the Galaxy and can provide invaluable constraints on planet formation theory. In this talk, Cieza will review observational studies of the structure and evolution of protoplanetary disks at infrared and (sub)millimeter wavelengths with an emphasis on recent transformational results from the Atacama Large Millimeter Submillimeter Array (ALMA) in northern Chile.