Everything in the world is made up of cells. Our bodies, the world around us, and everything we see is made up of cells. Cells are very small, we cannot see them with our eyes. However, we can see them using a microscope.

Cells come in two types: living cells and non-living cells. Living cells make up living things. Non-living cells do not make up living things.

Living Cells

Living cells make up living things. Living cells have important parts, including:

- Membrane: The membrane is a thin layer that surrounds the cell. It protects the cell from the outside environment.

- Nucleus: The nucleus is the control center of the cell. It contains the cell's DNA and RNA.

- Cytoplasm: The cytoplasm is the rest of the cell. It contains all of the other parts of the cell.

Non-living Cells

Non-living cells do not make up living things. Non-living cells come in two types: single-celled and multicellular.

- Single-celled: Single-celled organisms are made up of a single cell. For example, bacteria is a non-living cell made up of a single cell.

Forces

Forces are what make things move. There are many different types of forces, including:

- Gravitational force: Gravitational force is the force that pulls objects towards each other. It is the force that keeps us on the ground.

- Electromagnetic force: Electromagnetic force is the force that holds atoms together. It is the force that allows us to see, feel, and touch things.

- Strong force: Strong force is the force that holds protons and neutrons together in the nucleus of an atom.

- Weak force: Weak force is the force that causes radioactive decay.