Throughout time “fundamental” meant various things in different disciplines. For instance in physics, the ancient cultures Greece and India prior to the advent of structural physics, the atom was thought to be the fundamental particle of matter. They were trying to answer questions of philosophy and theology. Experimentation was crude and the equipment for examination and experimentation did not exist so these were what we now call thought experiments. It was not until the 19th century, some 500 years from the start of the Renaissance, that we were able to develop equipment that could provide crude measurements of predicted phenomena. However it was not until the latter half of the 19th century that it was discovered that the atom (which was until then considered “fundamental”) was found to consist of an electron and a nucleus and therefore not fundamental at all. Things when downhill (or uphill) from there at the end of the 19th and beginning of the 20th century, and today we have the Standard Model of physics which is our best current understanding of the universe. One should note: it has holes.
Henri Vonn De Roule