Same in optics, for resolve small target’s detail, we need a smaller ‘wavelength’.
According to de-Broglie, a matter has wavelength:
Therefore, a smaller wavelength requires larger momentum and momentum is related with energy by:
Thus, that’s why particle physics need larger and larger machines to produce higher and higher energy.
To reach 1 fm , electron should has kinetic energy around 100MeV, or momentum around 100MeV/c.
From Heisenberg’s uncertainty principle,
Therefore, to reach x ~ 1 fm, momentum should at least 200 MeV/c.
The above estimations are consistence.