Write a note on $DDT$.

(N/A) $DDT$ (p,p'-dichlorodiphenyltrichloroethane) is the first chlorinated organic insecticide.
It was originally prepared in $1873$,but its effectiveness as an insecticide was discovered in $1939$ by Paul Muller of Geigy Pharmaceuticals in Switzerland.
For this discovery,Paul Muller was awarded the Nobel Prize in Medicine and Physiology in $1948$.
The chemical structure of $DDT$ is as follows:
(Structure: Two chlorobenzene rings attached to a central carbon atom,which is also bonded to a hydrogen atom and a trichloromethyl group $-CCl_3$).