We know that most stars, if not all, were once surrounded by protoplanetary disks. How these young disks evolve into planetary systems is a fundamental question in astronomy. Observations of T Tauri stars (TTS) may provide insights into this question, particularly a subset of TTS with “transitional disks.” The spectral energy distributions of these objects feature an infrared "dip," indicating that they have developed holes or gaps in their dust disk. For many transitional disks, the inward truncation of the outer dust disk has been confirmed, predominantly through (sub)millimeter interferometric imaging. Many researchers have posited that these holes and gaps are the “footprints” of planets given that theoretical simulations predict that a young, forming planet will clear the material around itself, leaving behind a cavity in the disk. In this talk, I will review the key observational constraints on the dust and gas properties of transitional disks and examine these in the context of theoretical planet-induced disk clearing models. I will also discuss possibilities for future work in this field in the era of ALMA.