When I read about string theory, I sometimes get a feeling that the pointlike nature of particles in QFT is a problem that needs to be fixed, but I have never seen an explanation of the problem. Is this correct, and if so, why? Point in case (from https://en.wikipedia.org/wiki/String_theory): In physics, string theory is a theoretical framework in which thepoint-like particles of particle physics are replaced by one-dimensional objects called strings. And just to be sure, what does it mean that elementary particles are point-like in the first place? Does it mean anything besides that the particle has no internal structure? Because clearly the wave function is not point-like (although the position operator's eigen states are).