The HIV virion (viral particle) is a sphere that is roughly 140 nm in diameter. What particular kind of microscope is required to visualize an HIV virion and what is the basis of this microscope's ability to provide the resolution required to visualize HIV virions.

Electron microscope

Explanation:

Electron microscope uses a beam of electrons as energy source. Since the beam has an exceptionally short wavelength, it strikes most objects in its path and increases the resolution of the microscope significantly. Thus it has a higher magnification and resolution.