Media Composition - Components of media for the growth of plant callus and suspension cultures can be classified into five groups. The division usually reflects the way in which stock solutions are prepared and stored. These groups are:
i) inorganic nutrients (macronutrients and micronutrients)
 ii) organic supplement (vitamins)
iii) carbon source
 iv) growth regulators
v) gelling agent.
Some tissues are grown on simple media containing only inorganic salts and utilizable carbon (sugar) source, but for most others it is essential to supplement the medium with vitamins, amino acids and growth substances. Very often, complex nutritive substances are added to the medium. Such a medium, composed of "chemically defined" compounds, is referred to as a "synthetic" medium.