What is the smallest unit of life?

The smallest unit of life is the cell. Cells are considered the basic building blocks of all living organisms. Every living thing, whether it is a single-celled organism like bacteria or a complex multicellular organism like a human, is made up of cells. They perform essential functions necessary for life, including metabolism, energy production, growth, and reproduction.

While tissues, organs, and organisms are all crucial components of biological systems, they are made up of collections of cells. Tissues are groups of similar cells working together, organs are made up of different types of tissues, and an organism is a complete individual made up of various organs and systems. Thus, the cell is the fundamental unit that defines life, which makes it the correct answer to the question.