"Observations of protostellar disks suggest that planets formation may start early, in disks of ≤105 yr. The physical and chemical properties of young disks are strongly influenced by the intense and variable accretion/ejection activity, and by the interaction with the environment. The disk gains mass rapidly from the infalling envelope, as well as from accretion streamers. Because of the high accretion rate, young disks are warm and the snowlines are pushed outwards, with important implications for the growth of dust grains and the composition of the nascent planets. Accretion streamers and the shocks occurring where the streamer hits the disk, can drastically alter the disk's kinematical structure, mass budget, stability, and chemical composition. In addition, recent models and observations suggest that disk-winds can transport large grains from the inner disk to the envelope. The possible fallback of the grains in the outer disk regions would then promote dust growth and mixing in the disk, with crucial effects on the formation and composition of planets. I will review the physical and chemical properties of protostellar disks, and how these are affected by environmental and accretion/ejection processes."