The properties of interstellar clouds and the processes of star formation are studied by different means, both observationally, with a range of observational techniques from optical and infrared imaging to radio astronomy, and by numerical modelling. The properties and physics of very young stars, like T Tauri stars, and their circumstellar environments are investigated and considered in the context of evolutionary scenarios for the formation of stars and planetary systems.
Theories are developed for the formation of binary stars, including their interactions with gaseous protostellar disks, and of the dust disks surrounding stars. The physics of the apparently co-existent mass-gathering infall and angular momentum-shedding mass outflows is important also for the formation of planets. The origins of the recently discovered planets around other suns are investigated.