This question has several aspects.
- The electron’s size: No experiment has ever been conducted to determine the electron’s size. The electron is therefore the best possible realization of a “point particle”. Hence, it is unlikely that anything can be “seen”.
- Wavelength of radiation to be used: Again, this is dependent on the “size of the electron. To “see” any particle, let XYZ-wave be used (hypothetical). Optics will tell us that the wavelength should correspond to the dimensions of the particle. The wavelength of the particle can be reduced by increasing its energy. This allows us to see smaller particles. Because electron doesn’t have dimensions, it is impossible to determine how far to reduce the wavelength to make it comparable to its “size”.
A decrease in wavelength or an increase in energy can lead to another problem. An electron’s energy is increased if it has high levels of energy. It will be difficult to measure the size and speed of very fast-moving electrons. However, I don’t believe that there is any theoretical limit to the size measurement experiment.
If you are thinking of viewing electrons using visible lights (just like we do in our everyday lives), then it is important to know that the wavelength of visible lighting lies between 0.4m and 0.8m. The nucleus is 10,000,000 times smaller than the wavelength of visible sunlight. I don’t (probably not anyone) know how small the electron is relative to visible light.
It is my hope that it will help.