Title: Cell theory
Content: 1) All living organisms are composed of one or more cells. ; 2) The cell is the basic unit of structure and organization in organisms. ; 3) Cells arise from pre-existing cells.  In biology, cell theory is a scientific theory first formulated in the mid-nineteenth century, that living organisms are made up of cells, that they are the basic structural/organizational unit of all organisms, and that all cells come from pre-existing cells. Cells are the basic unit of structure in all organisms and also the basic unit of reproduction. The three tenets to the cell theory are as described below: The theory was once universally accepted, but now some biologists consider non-cellular entities such as viruses living organisms, and thus disagree with the first tenet. As of 2021: "expert opinion remains divided roughly a third each between yes, no and don’t know". As there is no universally accepted definition of life, discussion will continue.
Title: Cell theory
Content: 1) All known living things are made up of one or more cells ; 2) All living cells arise from pre-existing cells by division. ; 3) The cell is the fundamental unit of structure and function in all living organisms. ; 4) The activity of an organism depends on the total activity of independent cells. ; 5) Energy flow (metabolism and biochemistry) occurs within cells. ; 6) Cells contain DNA which is found specifically in the chromosome and RNA found in the cell nucleus and cytoplasm. ; 7) All cells are basically the same in chemical composition in organisms of similar species. The generally accepted parts of modern cell theory include: 
Title: Biology
Content:  Cell theory states that cells are the fundamental units of life, that all living things are composed of one or more cells, and that all cells arise from preexisting cells through cell division. Most cells are very small, with diameters ranging from 1 to 100 micrometers and are therefore only visible under a light or electron microscope. There are generally two types of cells: eukaryotic cells, which contain a nucleus, and prokaryotic cells, which do not. Prokaryotes are single-celled organisms such as bacteria, whereas eukaryotes can be single-celled or multicellular. In multicellular organisms, every cell in the organism's body is derived ultimately from a single cell in a fertilized egg.
Title: Life
Content:  Cells are the basic unit of structure in every living thing, and all cells arise from pre-existing cells by division. Cell theory was formulated by Henri Dutrochet, Theodor Schwann, Rudolf Virchow and others during the early nineteenth century, and subsequently became widely accepted. The activity of an organism depends on the total activity of its cells, with energy flow occurring within and between them. Cells contain hereditary information that is carried forward as a genetic code during cell division. There are two primary types of cells. Prokaryotes lack a nucleus and other membrane-bound organelles, although they have circular DNA and ribosomes. Bacteria and Archaea are two domains of prokaryotes. The other 
Title: Cell theory
Content: 1. All living organisms are composed of one or more cells ; 2. The cell is the most basic unit of life 3. All cells arise only from pre-existing cells Credit for developing cell theory is usually given to two scientists: Theodor Schwann and Matthias Jakob Schleiden. While Rudolf Virchow contributed to the theory, he is not as credited for his attributions toward it. In 1839, Schleiden suggested that every structural part of a plant was made up of cells or the result of cells. He also suggested that cells were made by a crystallization process either within other cells or from the outside. However, this was not an 
Title: Outline of cell biology
Content: Cell &ndash; The structural and functional unit of all known living organisms. It is the smallest unit of an organism that is classified as living, and also known as the building block of life. Cell comes from the Latin cellula, meaning, a small room. Robert Hooke first coined the term in his book, Micrographia, where he compared the structure of cork cells viewed through his microscope to that of the small rooms (or monks' "cells") of a monastery. ; Cell theory &ndash; The scientific theory which states that all organisms are composed of one or more cells. Vital functions of an organism occur within cells. All cells come from preexisting cells and contain the hereditary information necessary for regulating cell functions and for 
Title: Life
Content:  cell is considered the structural and functional unit of life. There are two kinds of cells, prokaryotic and eukaryotic, both of which consist of cytoplasm enclosed within a membrane and contain many biomolecules such as proteins and nucleic acids. Cells reproduce through a process of cell division, in which the parent cell divides into two or more daughter cells. In the past, there have been many attempts to define what is meant by "life" through obsolete concepts such as Odic force, hylomorphism, spontaneous generation and vitalism, that have now been disproved by biological discoveries. Aristotle is considered to be the first person to classify organisms. Later, Carl Linnaeus introduced his system of binomial nomenclature for the classification of species. 
Title: Cell (biology)
Content:  The cell is the basic structural and functional unit of life. Every cell consists of a cytoplasm enclosed within a membrane, which contains many biomolecules such as proteins and nucleic acids. Most plant and animal cells are only visible under a light microscope, with dimensions between 1 and 100 micrometres. Electron microscopy gives a much higher resolution showing greatly detailed cell structure. Organisms can be classified as unicellular (consisting of a single cell such as bacteria) or multicellular (including plants and animals). Most unicellular organisms are classed as microorganisms. The number of cells in plants and animals varies from species to species; it has been 
Title: Cell biology
Content:  Cells were first seen in 17th century Europe with the invention of the compound microscope. In 1665, Robert Hooke termed the building block of all living organisms as "cells" (published in Micrographia) after looking at a piece of cork and observing a cell-like structure, however, the cells were dead and gave no indication to the actual overall components of a cell. A few years later, in 1674, Anton Van Leeuwenhoek was the first to analyze live cells in his examination of algae. All of this preceded the cell theory which states that all living things are made up of cells and that cells are the functional and structural unit of organisms. This was ultimately concluded by plant scientist, Matthias Schleiden and animal scientist Theodor Schwann in 1838, who viewed live cells in plant and animal tissue, respectively. 19 years later, Rudolf Virchow further contributed to the cell theory, adding that all cells come from the division of pre-existing cells. Viruses are not considered in cell biology – they lack the characteristics of a living cell, and instead are studied in the microbiology subclass of virology.
Title: Cell theory
Content:  enter the egg cell. This put an end to the previous theory of spontaneous generation. After reading letters by Leeuwenhoek, Hooke was the first to confirm his observations that were thought to be unlikely by other contemporaries. The cells in animal tissues were observed after plants were because the tissues were so fragile and susceptible to tearing, it was difficult for such thin slices to be prepared for studying. Biologists believed that there was a fundamental unit to life, but were unsure what this was. It would not be until over a hundred years later that this fundamental unit was connected to cellular 

Question: what is the most fundamental unit of life according to the cell theory?
Answer: cells.