What type of organisms can a microscope help visualize?

A microscope is an essential tool in microbiology and other biological sciences for visualizing smaller organisms that cannot be seen with the naked eye. This includes cells, bacteria, fungi, and viruses.

The correct answer reflects the microscope's capability to magnify small organisms, allowing scientists and researchers to observe fine details and structure that are critical for understanding their biology and behavior. For instance, when studying viruses, specialized imaging techniques like electron microscopy are used, as their size is well below what conventional light microscopy can resolve.

In contrast, large mammals and insects are easily observable without a microscope due to their size. Plant cells, while they can be viewed with a microscope, are not the only type of cells that can be observed; animal cells and various microorganisms can also be visualized. Lastly, atmospheric particles are typically studied using different techniques such as air samplers and chemical analysis rather than microscopy. Thus, the choice emphasizing small organisms like viruses accurately captures the primary function of a microscope in scientific observation.