Hairy root cultures, induced by A. rhizogenes Ri-T-DNA integration, are genetically stable (chromosomally integrated), grow rapidly without exogenous phytohormones, and produce root-specific secondary metabolites (alkaloids, terpenoids, flavonoids) at levels comparable to or exceeding the intact plant. They can be scaled up in bioreactors (e.g. mist reactors, bubble columns). They are used to produce scopolamine, hyoscyamine, taxol intermediates, and other high-value compounds.