With more than 3000 detected exoplanets it is now clear that planet formation is a natural outcome of stellar
formation. However, the mechanisms by which planets do form remain uncertain. The most promising way to understand
this process is to study protoplanetary disks that show signposts of planet formation: the so-called transitional
disks. In this talk I will first introduce the observational techniques and instruments that are revolutionizing this field
I will finish presenting ALMA and SPHERE/VLT observations of transitional disks around low-mass stars
that, according to our current understanding, show evidences of planet-disk interactions.