Why is the cahrge on an electron cosidered as the smallest measurable unit of electricity?

Explanation

Americal scientist, R.A. Millikan determined the cahrge of an electron by his famous classical oil drop experiment. The value was found to be `4.8xx10^(-10)` esu or `1.602xx10^(-19)`C. No other particles carry a lesser negative charge. This is the smallest measurable quantity of charge. the electric charge carried by positively or negatively charged particles are integral multiples of this minimum possible quantity. hence, the charge of an electron is considered as the smallest unit of electricity.