Cells & Microorganisms
From the levels of biological organization to the gut microbiome you carry around with you. Biology at the microscopic scale.
Every multicellular organism — from a redwood to a blue whale to you reading this — is a colony of cells working together. The first ~2 billion years of life on Earth were entirely microbial. Even now, the vast majority of living things on the planet are single-celled. Cells and microorganisms are not a peripheral topic in biology; they are the base case.
Articles in this cluster
From Cells to Superorganisms
Levels of biological organization — molecules, cells, tissues, organs, organisms, populations, ecosystems — and why each level has its own rules.
The Microbial World
Bacteria, archaea, protists, fungi. The invisible majority of life on Earth — what they do for us, what they do to us.
Understanding Viruses
What viruses actually are, how they replicate, why some are mostly harmless and others spark pandemics.
Mitosis and Meiosis: How Cells Divide
The two completely different jobs of cell division — one for growth and repair, one for making eggs and sperm.
The Gut Microbiome
About 38 trillion microbes living in your gut, doing real work on your behalf every day.
How to read this cluster
Start with From Cells to Superorganisms — it gives you the levels-of-organization frame that the rest of biology depends on. If you want the practical impact: The Microbial World and Understanding Viruses explain why microbiology matters for medicine and agriculture.
Related sub-pillars
Return to the main Biology resources hub · Browse: cells · cell biology · microbiology · viruses