  This article summarizes a Splinter Session at the Cool Stars XV conference in
St. Andrews with 3 review and 4 contributed talks. The speakers have discussed
various approaches to understand the structure and evolution of the gas
component in protoplanetary disks. These ranged from observational spectroscopy
in the UV, infrared and millimeter, through to chemical and hydrodynamical
models. The focus was on disks around low-mass stars, ranging from classical T
Tauri stars to transitional disks and debris disks. Emphasis was put on water
and organic molecules, the relation to planet formation, and the formation of
holes and gaps in the inner regions.
