By Kimberley Collins 03/08/2016

Take a journey through the microscopic world of a cell as these GIFs, taken from a video by NPR, show how the flu spreads through your body. 

Viruses can’t survive by themselves and must seek out a living host to grow and multiply. They spread very easily and enter our bodies through the nose, mouth or breaks in the skin.

Once they’re inside, they look for cells to infect. Cold and flu viruses will often attack cells that line the respiratory or digestive tracts.

Each virus is covered in small molecular receptors that act as keys. If they fit the receptors on a cell, it will open and let in in the entire virus or accept its genetic material.

Once inside the cell, the protein capsule on the virus bursts and releases the genetic material.

The virus takes over the host cell’s machinery and uses it to make copies of its own genetic material, along with proteins to form new viruses.

Soon, millions of new copies of the virus are floating around the cell until they’re ready to be released to infect another host cell. They will either burst the host cell and spread or be enveloped in the host cell’s membrane.

The new viruses spread quickly and begin attacking other cells in your body. Once a single virus enters a cell, it can produce thousands of new viruses.

But fear not! Your immune system is alerted and comes quickly to the rescue. White blood cells called phagocytes ingest the viruses and slurp them up in a process called phagocytosis.

Chemicals called pyrogens cause your body temperature to increase, giving you get a fever that actually helps to fight the virus. Most of the chemical reactions that happen in your body have an optimal temperature – 37 degrees celsius, or 98.6 degrees fahrenheit. When your temperature rises, the reactions slow down and rate of viral reproduction decreases.

This immune response continues until the viruses are gone from your body.

This post was originally featured on Buzzfeed.