Final answer:
Viruses are acellular, microscopic entities much smaller than bacteria and can only be viewed with an electron microscope.
Step-by-step explanation:
Viruses are indeed acellular, microscopic, and much smaller than bacteria. These infectious agents require an electron microscope for visualization and consist of a nucleic acid core, either DNA or RNA.
Viruses do not have a cellular structure and hence are termed acellular. An important characteristic is their reliance on a host cell to replicate, as they cannot do so outside of a cellular environment. Viruses can infect a multitude of organisms, ranging from bacteria and plants to animals.
In terms of size comparison, bacteria are generally around 100 times larger than viruses, which means that viruses are significantly smaller than bacteria and cannot be observed under a regular light microscope.