The basic unit of life is called a "cell." Cells are the smallest structural and functional units that make up all living organisms. They can exist as single-celled organisms, like bacteria, or as multi-cellular organisms, such as plants and animals. Cells perform various vital functions, including metabolism, energy production, growth, and reproduction. They contain specialized structures called organelles that carry out specific tasks, such as the nucleus (which houses genetic material) and mitochondria (which produce energy). The study of cells, known as cell biology, is crucial for understanding life processes and how organisms function.