Cells: the tiny building blocks of living things — Biology, 7–10 years
Every plant and animal is made of cells. Cells are too small to see without a microscope, but together they make bodies grow, work and repair themselves.
A body is built from cells
A cell is a tiny living part, like one small room in a huge building. A human body has many kinds of cells: muscle cells help movement, nerve cells carry messages, and skin cells make a covering. Plants also have cells.
Why look for cells?
People once saw that plants and animals were made of tissues, but they could not tell what those tissues were made of. Microscopes revealed tiny repeated parts: cells. This solved a puzzle about how a whole body can grow and repair a small cut.
Worked example: seeing onion cells
Place a thin onion skin on a slide, add a drop of stain and cover it with glass. Under a microscope, start on low power, then magnify. You may see rows of box-like cells: one small piece of onion is made of many living units.
Trap: one cell is a tiny animal
It is easy to imagine every cell as a tiny version of a person or animal, because cells are alive. Most cells do not have eyes, legs or thoughts, though. They have particular jobs and work together; a single cell is only one small part of a larger living body.
Cells outside the classroom
Doctors and scientists study cells to understand illnesses and healing. A blood test can examine cells, and a microscope can help identify what is happening in a sample. Cell knowledge also helps farmers and gardeners understand how plants grow.
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