Cell Theory
All living things are made of cells, and every cell comes from another cell.
About this topic
Cell theory is one of biology's foundations. It states that all living things are made of one or more cells, the cell is the basic unit of structure and function, and all cells come from pre-existing cells. It was developed by Schleiden, Schwann and Virchow in the 1800s following the invention of the microscope.
Modern additions say cells carry hereditary information (DNA) and that energy flow happens within cells. Unicellular organisms are a whole living thing in one cell, while humans have trillions.
Imagine looking at a thin slice of onion skin under a microscope: you see neat brick-like units, each one a cell. Robert Hooke first named cells in 1665 looking at cork, and later scientists realised every plant and animal they examined was built the same way. Virchow's idea that cells come only from other cells ended the old belief in spontaneous generation, which claimed that maggots arose from rotting meat.
Cell theory underpins modern medicine: cancer is understood as cells dividing out of control, infections as foreign cells invading, and tissue engineering as growing cells in a lab. Students often think viruses disprove cell theory because they are not cells; this is exactly why many biologists debate whether viruses count as living. Remember that the theory describes cells as the basic unit, not that every organism is microscopic.
Key ideas
- Cells are the basic unit of life
- Proposed by Schleiden, Schwann and Virchow
- Cells arise by division
Quick check
Use cases: where Cell Theory helps
- Homework: review the key idea behind Cell Theory before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Cell Theory without notes.
- Visual learning: play with the interactive lab to see how Cell Theory changes when you adjust its inputs.
- Teaching a friend: explain Cell Theory in your own words, then compare your version with the key ideas.
Biology underpins medicine, farming, conservation and biotechnology.
Frequently asked questions
What is Cell Theory?
All living things are made of cells, and every cell comes from another cell.
What will I learn in Cell Theory?
Cells are the basic unit of life. Proposed by Schleiden, Schwann and Virchow. Cells arise by division.
Is Cell Theory part of Biology?
Yes. It is one of 150 Biology topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Cell Theory lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Cell Theory?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.