These biology mini-lessons are illustrated with interactive Web animation. The Adobe Flash plug-in is required for these click and learn features. Download it free from Adobe.com.

Immunology primer

An overview of the immune system, concentrating on the roles played by B and T lymphocytes, and the antigen-presentation system. Also featured on the recently released HHMI DVD, AIDS: Evolution of an Epidemic, available free from HHMI. Order DVDs here.

Retroviruses and viral diversity

A brief discussion of what makes a virus a retrovirus, and how they differ from other types of viruses. Also featured on the recently released HHMI DVD, AIDS: Evolution of an Epidemic, available free from HHMI. Order DVDs here.

Regeneration: Evolution and Medicine

An overview and comparison of different regenerative capabilities in many different organisms. Also featured on the HHMI DVD Potent Biology: Stem Cells, Cloning, and Regeneration, available free from HHMI. Order DVDs here.

Stem Cell Therapies Today

An exploration of current and future therapies. Also featured on the HHMI DVD Potent Biology: Stem Cells, Cloning, and Regeneration, available free from HHMI. Order DVDs here.

Visualizing Gene Expression

Learn about the different ways scientists are able to detect when genes are being expressed in various tissues. Also featured on the HHMI DVD Evolution: Constant Change and Common Threads, available free from HHMI. Order DVDs here.

RNA Interference

RNA interference is an exciting new research tool for shutting down genes. It could also yield new medical treatments. Learn how RNA interference was discovered and how it works. Also featured on the HHMI DVD The Double Life of RNA, available free from HHMI. Order DVDs here.

RNA Diversity

RNA is an information molecule that can also function as an enzyme. Learn about the many different forms that RNA can take. Also featured on the HHMI DVD The Double Life of RNA, available free from HHMI. Order DVDs here.

Telomeres Revisited

This mini-lesson covers the research on telomeres that has happened since the 1995 Holiday Lectures. Also featured on the HHMI DVD The Double Life of RNA, available free from HHMI. Order DVDs here.

Measuring Obesity

There is no way to directly measure how much fat a living person has. Learn about the various methods used by researchers and fitness advisors to estimate a person’s body fat. Also featured on the HHMI DVD Science of Fat, available free from HHMI. Order DVDs here.

Molecular Structure of Fat

Fat is tissue, a type of cell, and a substance. Learn about the chemical and molecular structure of fat and how it relates health. A Flash slide show that delves into the various molecular shapes that fat can take. Also featured on the HHMI DVD Science of Fat, available free from HHMI. Order DVDs here.

How The Body Uses Fat

A Flash slide show that delves into the various molecular shapes that fat can take. Also featured on the HHMI DVD Science of Fat, available free from HHMI. Order DVDs here.

p53: The Guardian of the Genome

One of the most important molecules relating to cancer is called p53. It has been called the guardian of the genome. Learn about what p53 does, and how interfering with its function can lead to cancer. Also featured on the HHMI DVD Learning from Patients: The Science of Medicine, available free from HHMI. Order DVDs here.

Structure of the Proteasome

The proteosome is a large molecular machine that plays an important role in recycling and regulating cellular proteins. Learn about the structure and function of this fascinating cellular machine. Also featured on the HHMI DVD Learning from Patients: The Science of Medicine, available free from HHMI. Order DVDs here.

Analyzing Microarray Data

DNA microarrays, or gene chips, are an important new technology for genomic research. Learn how researchers use computing to analyze and interpret the huge datasets generated by microarray experiments. Also featured on the HHMI DVD Scanning Life's Matrix: Genes, Proteins, and Small Molecules, available free from HHMI. Order DVDs here.

Origins of Modern Humans

All living humans originated from populations of ancestors who migrated out of Africa less than 100,000 years ago. Learn how scientists have used genetic markers to trace the migration routes and origins of modern human populations. Also featured on the HHMI DVD Scanning Life's Matrix: Genes, Proteins, and Small Molecules. Available free from HHMI. Order DVDs here.

Molecular Menagerie

Small molecules are chemicals that can interact with proteins to affect their functions. Learn about the structure and biological functions of various small molecules like sugar and caffeine. Also featured on the HHMI DVD Scanning Life's Matrix: Genes, Proteins, and Small Molecules. Available free from HHMI. Order DVDs here.

Gender Testing of Athletes

At times those responsible for conducting high-stakes athletic competitions like the Olympics have been greatly concerned with gender testing athletes. Learn why verifying a person's gender may be harder than you think.

Antibiotics Attack

A multimedia presentation covering how antibiotics function to fight invaders. Five major sections with animations cover bacteria, antibiotic structure, pathways of attack, penicillin, and antibiotic resistance.

Bacterial Conjugation

Watch this Flash animation to see how bacteria share genes that encode resistance to antibiotics.

Viral Subunit Reassortment

Watch this Flash animation to see how different viral strains can be generated by a process called subunit reassortment.

Viral Infection Mechanism

Watch this Flash animation to see how viruses are studied in the lab.

The Vertebrate Circulatorium

In the Veterbrate Circulatorium you can compare the circulation patterns of different vertebrates. Click on the different animal names on the left to see the overall circulation patterns in "systemic view." More detailed views of the hearts are available by clicking on "To heart detail."

Electrocardiogram Primer

A quick tutorial on the basics of the electrocardiogram machine. Created by one of HHMI's high school interns from Thomas Edison High School of Technology in Montgomery County, Maryland.

Heart Size in Mammals

Explore the relationship between heart size and rate in this multimedia demonstration by one of HHMI's high school interns from Thomas Edison High School of Technology in Montgomery County, Maryland.

Electric Fish

You're probably thinking of an electric eel, sending out 800 volts of electricity—enough to stun or kill a person, even a horse.

But most species of electric fish live in fresh water and are actually harmless. They generate from only a fraction of a volt up to a few volts of electricity with their electric organs located in the tail, which is made up of specialized muscle or nerve tissue.