Cryosol: Cryosol, one of the 30 soil groups in the classification system of the Food and Agriculture Organization (FAO). Cryosols are characterized by frozen soil ... Britannica.com
Robert A. Millikan's Definitive Measurement. Robert A. Millikan started his work on electron charge in 1906 and continued for seven years. His 1913 article announcing the determination of the electron's charge is a classic and Millikan received the Nobel Prize for his efforts.
A proton has a charge of +e, while an electron has a charge of-e. Electrons and protons are not the only things that carry charge. Other particles (positrons, for example) also carry charge in multiples of the electronic charge. Those are not going to be discussed, for the most part, in this course, however.