Production of useful secondary metabolites and regeneration of useful plants are attracting extensive interest from investigators of plant cell culture. In this short review, recent developments in the application of plant cell culture system are described referring to the works of the author＇s group. Regarding callus culture producing secondary metabolites, the following topics are described: 1. two-stage culture, 2. conditioning effect, 3. kinetic structured model, 4. immobilization, and 5. reactors. Production of useful substances with hairy root culture is also effective and described in this review. Regeneration of plants contributes to production of food and to afforestation. Production of somatic embryos and artificial seeds is described as well.