I see that we use dimensional analysis involving constants of nature to obtain the Planck length and then apply the uncertainty principle to find the corresponding Planck mass-energy. But the energy and length scales were found by invoking a "particle" interpretation of fundamental entities of nature. Wasn't it? This is not still clear for me, I mean, where and how we used the notion of particles to obtain Planck scales? I am not deep into the quantum field theory yet, but if we let go of the notion of particles and introduce the fields (real or complex set of functions of spacetime) instead as the fundamental entities of nature, then can we make sense of arbitrarily large energies or small distances? But gravity does not still have any valid QFT, it is now a classical theory, so we say for arbitrarily small distances on space, there should be only quantum fields, and therefore we are waiting for quantum gravity? Am I right in the above argument?