Sandalwood or Heartwood is the complete wood where the tree deposits secondary metabolites — in this case, its fragrant yellow viscous oil. 

The best wood comes from trees over 60 years old. Sandalwood has been a source of valuable wood and aromatic oil since the fifth century B.C. 

The essential oil of the plant is derived through steam distillation of Sandalwood and has the aroma of aged wood.