Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

[Q]: A electron microscope is used to see extremely small objects.
[A]: What type of microscope is used to see extremely small objects?

[Q]: Wave amplitude and wavelength are two important measures of wave size.
[A]: Wave amplitude and wavelength are two important measures of what?

[Q]: Saturn is made mostly of helium and hydrogen.
[A]:
Saturn is made mostly of helium and what else?