AbstractRecent progress in astrochemistry of low-mass protostellar sources is reviewed. In particular, we focus on disk formation processes and associated chemical changes at a 50 au scale, which is extensively being studied with ALMA. A small scale chemical differentiation sensitively reflects changes in physical conditions, and hence, it provides us with unique opportunities of chemical diagnostics of disk-forming regions. Complex physical and chemical pictures of disk formation revealed by observations are summarized, and future prospects are discussed.