Rubber from Hevea brasiliensis, known as natural rubber (NR), contains rubber hydrocarbon and ca. 6% of non-rubber components. The biosynthesis of the NR latex particles takes place in the laticifers of the Hevea rubber tree. Rubber molecule is synthesized by the addition of isopentenyl diphosphate into farnesyl diphosphate, the initiating molecule, catalysed by rubber transferases (EC 188.8.131.52). The rubber molecule is known to be composed of a long polymer chain with branched points. The fundamental chain was found to be consisting of a long sequence of cis-1,4-isoprene units having two trans-1,4-isoprene units at the initiating terminal. Both initiating- and terminating-terminal of rubber molecules and the branching formation will be discussed in detail.