The cytoskeleton is a collection of fibers that gives shape and support to cells, like the skeleton does for our bodies. It also allows movement within the cell and, in some cases, by the entire cell. Three different types of fibers make up the cytoskeleton: actin filaments, intermediate filaments, and microtubules.

Powering Muscles

Actin filaments contract or lengthen to give cells the flexibility to move and change shape. Along with the protein myosin, they’re responsible for muscle contraction, including voluntary movement and involuntary muscle contractions, such as our heartbeats. Actin filaments are the thinnest and most brittle of the cytoskeletal fibers, but they’re also the most versatile in terms of shape.

The tiny roundworm Caenorhabditis elegans is one of the most common research organisms—creatures scientists use to study life. While C. elegans may seem drastically different from humans, it shares many genes and molecular pathways with us. Viewed with a microscope, the worm can also be surprisingly beautiful. Aside from the stunning imagery, these examples from our Image and Video Gallery show how C. elegans helps scientists advance our understanding of living systems and find new ways to improve our health.

Credit: Keir Balla and Emily Troemel, University of California San Diego.

This C. elegans has been infected with microsporidia (purple), parasites closely related to fungi. The yellow shapes are the worm’s gut cells, and the blue dots are nuclei. Some microsporidia can infect people, so studying the parasites in worms could help researchers devise strategies to prevent or treat infections.

NIGMS, in collaboration with Scholastic, has developed a collection of free biology and health activities on the educational app Kahoot! You can play them alone, with friends, or with a class of students. Four Kahoots! are currently available:

• Imaging the Microscopic World investigates how researchers view cells, proteins, and other tiny structures.
• Superbugs delves into infectious bacteria and viruses that can’t be fought off with medicines.
• The Science of Sleep explores biological clocks and circadian rhythms.
• Regeneration highlights how animals replace or restore damaged or missing cells, tissues, organs, and even entire body parts.

A cross-section of a cell showing organelles. Credit: Judith Stoffer.

Welcome to our tour of the cell! Imagine you’ve shrunk down to about 3 millionths of your normal size. You are now about 0.5 micrometers tall (a micrometer is 1/1,000th of a millimeter). At this scale, a medium-sized human cell looks as long, high, and wide as a football field. But you can’t see nearly that far. Clogging your view is a rich stew of molecules, fibers, and various cell structures called organelles. Like the internal organs in your body, organelles in the cell each have a unique biological role to play.

The Nucleus and Its Closest Neighbor

Our first stop is the somewhat spherical structure about 50 feet in diameter. It’s the nucleus—basically the cell’s brain. The nucleus is the most prominent organelle and can occupy up to 10 percent of the space inside a cell. It contains the equivalent of the cell’s genetic material, or DNA.

Proteins play a role in virtually every activity in the body. They make up hair and nails, help muscles move, protect against infection, and more. Many NIGMS-funded researchers study the rich variety of proteins in humans and other organisms to shed light on their roles in health and disease.

Take our quiz to test how much you know about proteins. Afterward, find more quizzes and other fun learning tools on our activities and multimedia webpage, which includes an interactive protein alphabet.

Cover of Pathways student magazine.

NIGMS and Scholastic bring you our latest issue of Pathways, which focuses on imaging tools that help scientists unlock the mysteries of our cells and molecules. A better understanding of this tiny world can help researchers learn about the body’s normal and abnormal processes and lead to more effective, targeted treatments for illnesses.

Pathways is designed for students in grades 6 through 12. This collection of free resources teaches students about basic science and its importance to health, as well as exciting research careers.

We seldom see microscopic objects next to one another, so it can be difficult to picture how they compare. For instance, it might surprise you that a thousand cold-virus particles could line up across one human skin cell! The largest objects that scientists view through microscopes are about a millimeter (roughly the size of a poppyseed), and they’re about 10 million times larger than the smallest molecules scientists can view: atoms.

Some bacteria benefit us as part of our microbiome—the vast collection of microorganisms that live in and on our bodies—while others can make us sick. Whether helpful or dangerous, bacteria can appear colorful and striking under a microscope. These photos provide just a small peek into the incredible diversity of these microbes.

Credit: Liyang Xiong and Lev Tsimring, BioCircuits Institute, UCSD.

This floral pattern emerged when a researcher grew two strains of bacteria—Acinetobacter baylyi (red) and Escherichia coli (green)—together for 2 days in a petri dish. A. baylyi are found in soil and typically don’t pose a threat to humans, although some strains can cause infections. E. coli normally live in the intestines of people and animals. Most strains are harmless, but some can cause food poisoning or other illnesses.

Cells are the smallest units of life, providing structure and function for all living things, from microorganisms—like bacteria, algae, and yeast—to humans. They come in a wide range of sizes and shapes, and they’re complex machines with many smaller components that work together.

Some NIGMS-funded researchers use imaging techniques to peer inside cells, examine their structures, and study how they divide, grow, communicate, and carry out basic functions. Others use biochemical and genetic tests to study how cells interact with their environments, including those that may be toxic. Understanding cells’ biological processes helps to keep us healthy and identify new methods for treating disease.

Take our quiz to test how well you know cells. Afterward, check out our other blog posts on cell biology.

If you’re looking for ways to engage students in science this school year, NIGMS offers a range of free resources that can help. All of our STEM materials are online and print-friendly, making them easy to use for remote teaching.

Pathways , developed in collaboration with Scholastic, is aligned with STEM and ELA education standards for grades 6 through 12. Materials include:

• Student magazines with corresponding teaching guides
• Related lessons with interactives
• Videos
• Vocabulary lists

Cover of Pathways student magazine, third issue.

Available lessons examine basic science careers, regeneration, and circadian rhythms.