Cells are the basic structural, functional, and biological units of all known living organisms. A cell is the smallest unit of life that can replicate independently, and cells are often called the "building blocks of life".

Here are some key aspects of cells:

• Structure: Cells typically consist of a membrane enclosing a cytoplasm, which contains various biomolecules such as proteins, nucleic acids, and lipids.
• Function: Cells carry out all the functions necessary for life, including growth, metabolism, reproduction, and response to stimuli.
• Types: There are two main types of cells: Prokaryotic (bacteria and archaea) and Eukaryotic (protists, fungi, plants, and animals). Eukaryotic cells have a nucleus and other complex organelles, while prokaryotic cells do not.
• Cell Theory: The cell theory, a fundamental concept in biology, states that all living organisms are composed of one or more cells, the cell is the basic unit of life, and new cells arise from pre-existing cells.

For more detailed information, you can refer to these resources:

• National Center for Biotechnology Information - The Cell
• Nature Education - Cell Structure