On bigger bodies, I've learnt so far that charge is caused by a lack or excess of electrons or protons but when you look at an electron or proton, how are they charged? what is the cause of their charge?

On bigger bodies, I've learnt so far that charge is caused by a lack or excess of electrons or protons but when you look at an electron or proton, how are they charged? what is the cause of their charge?

If "charge" cannot be given a cause for particles such as electrons or protons, any plausible theories related to this cause are also welcome, if there are any.