Single-cell organisms, also known as unicellular organisms, are living entities that consist of only one cell. They can be found in various environments, including soil, water, and even inside other organisms. Examples of single-cell organisms include bacteria, archaea, and protozoa. These organisms perform all necessary life functions within that single cell, such as metabolism, reproduction, and response to stimuli. Despite their simplicity, single-cell organisms are incredibly diverse and can adapt to extreme conditions. They reproduce mainly through a process called binary fission, where one cell divides into two identical cells. Some single-cell organisms can also exchange genetic material through processes like conjugation, contributing to their adaptability and evolution.