What ist the use of the elementary charge of electrons ?

hello, as the title says, I am preparing a presentation for school where me and my friend explain the derivation of the calculation for the elementary charge of electrons. now we obv need to include the basic information about millikan etc. and at the end we also wanted to add the use of the value for e . now i couldnt find any real "use" for the elementary charge in today's life . could somebody help me out? please be gentle with my english since i am not familiar with english physics terms thanks a lot