Wavelengths

Long wavelength waves gently lift Mallard up and down but continue undisturbed by his presence. Phyllis, flying over the other side of the pond and detecting the waves, would not be able to tell that Mallard was in the way. In other words, long wavelength waves do not reflect off Mallard.
When the wavelength gets smaller, Mallard is tossed about more violently because shorter wavelength waves carry more energy. The waves themselves are modified by Mallard's presence and this time Phyllis would be able to tell that Mallard, or something, is out there on the pond.
It's just the same when it comes to tiny things. The smaller the object we want to study, the shorter the wavelength and the higher the energy of the probe we need to use. Electrons in an electron microscope have shorter wavelengths than visible light, which is why they can resolve smaller things. Visible light has wavelengths ranging from about 7 x 10-7 metres for red to about 4 x 10-7 metres for violet. Electrons in a typical electron microscope have wavelengths measured in picometres. One picometre is 10-12 of a metre, meaning that electron microscopes can resolve things hundreds of thousands of times smaller than optical microscopes.

Electron microscopes can resolve atoms, which are about 10-10 metres across. To get a glimpse of what is inside a proton, which is about 10-15 metres across, a wavelength of 10-16 metres would be needed.