The smallest unit of living matter is known as a cell. Cells are the basic building blocks of all organisms, ranging from unicellular bacteria to complex multicellular beings like plants and animals. Each cell contains various organelles that perform specific functions, such as energy production and waste removal. The study of cells, known as cell biology, is fundamental in understanding life processes, health, and disease mechanisms. Cells can also reproduce, allowing the growth and repair of tissues in multicellular organisms.