Understanding how stars and planets form requires observations at long wavelengths in order to penetrate their dusty natal clouds.  Thanks to its high sensitivity and resolution, Webb is a major step forward in studying the physical and chemical structure of protostars and protoplanetary disks. This talk will present an overview of recent results on gaseous and icy molecules, most notably from the MIRI guaranteed time programs JOYS and MINDS.  Water, CO2, C2H2 and a variety of simple and more complex organic species will be discussed. Together with related ALMA data, they point to a rich chemistry with a varying composition and C/O ratio that may -surprisingly!- be linked to stellar mass and to substructures in the planet-forming zones of disks.

Websites: miri.strw.leidenuniv.nl, minds.cab.inta-csic.es

recording: www.youtube.com/watch