Finding young planets in protoplanetary disks is essential for understanding planet formation process and constraining the long-term evolution of planetary systems. Transitional disks, protoplanetary disks with gaps and holes, are great candidates for harboring these young planets. However, recent near-IR polarization imaging (e.g. SEEDS, VLT) and submm (e.g. SMA, ALMA) observations have posed several puzzles on transitional disks. Such as, dust and gas seems to decouple in these disks and the decoupling can occur non-axisymmetrically in disks. Spiral patterns are also discovered in these disks. In the talk, I will first summarize recent theoretical and observational developments on transitional disks. Then I will present our hydrodynamic and magnetohydrodynamic global simulations which have considered dust particle dynamics and non-ideal MHD effects for the first time. By comparing such realistic simulations with observations, we have constrained protoplanetary disk properties and revealed the early stage of planet formation. Finally, I will discuss the observational strategies to directly find young planets in protoplanetary disks and suggest that accreting circumplanetary disks could be the key to detect young planets directly. Current direct imaging observations may have already found some circumplanetary disk candidates and there are more to come.