What are bacteria and viruses characterized as?

Bacteria and viruses are classified as microscopic organisms, which means they are too small to be seen without the aid of a microscope. Both of these entities can only be observed at a microscopic level, highlighting their tiny size compared to larger life forms.

Bacteria are single-celled organisms that can exist independently or in groups, while viruses are even smaller and consist of genetic material encased in a protein coat and cannot reproduce independently; they need a host cell to replicate. This microscopic characteristic is fundamental to understanding their biology and the way they interact with hosts and the environment, as well as their relevance in causing infections and diseases.

This understanding emphasizes that while they can lead to infections and health issues, they do not fit the descriptions of larger multicellular organisms, parasites that are visible to the naked eye, or non-infectious agents.