A cartoon of the multiwavelength view of a protoplanetary disk, from my paper ‘‘A “Rosetta Stone” for protoplanetary disks: The synergy of multi-wavelength observations’, by A. Sicilia-Aguilar, A. Banzatti, A. Carmona, et al., 2016, PASA 33, 59

And some more about protoplanetary disk evolution:

A young, accreting disk, made of well-mixed dust and gas.

Some grain coagulation and sedimentation are happening…

Transition object: the inner disk is optically thin, but there is still some accretion…

… until the accretion ceases.

Although the real case may look rather like:

How to make nice disks pictures? I did them in almost no time with
OpenOffice, plus some gimp to add accretion funnels and
other details.