Khan Academy
Khan Academy: Biology: Structure of a Cell: Introduction to Cells
Learn about cell theory in this article. [12:29]
CPALMS
Florida State University Cpalms: Florida Students: The Cell Theory
Learn how the Cell Theory defines living organisms.
Estrella Mountain Community College
Online Biology Book: Cells: Origins
Through full-color images and concise information, learn about the origin of cells. Discover some of the notable studies surrounding the history of life on Earth.
City University of New York
Exploring Life: The First Cells
A brief essay about older and more recent ideas on when the first cells evolved. Good coverage of different scientific theories about the origin of life.
Estrella Mountain Community College
Online Biology Book: The Nature of Science and Biology
Use the scientific reasoning and critical thinking to take an in-depth look at the basics of biology.