Cells are the basic building blocks of life, and all living organisms are composed of one or more cells. Bacteria are single-celled microorganisms that are the smallest and simplest form of life on Earth. They are so tiny that they can only be seen with a microscope.

Bacteria can be found in almost every environment on Earth, including soil, water, and air. Some bacteria are beneficial to us and play important roles in our daily lives, such as in the digestion of food and in the production of antibiotics, while others can cause diseases such as strep throat, pneumonia, and tuberculosis. It's important to remember that not all bacteria are harmful, and some are actually essential for our survival.