Microscopes are really useful for looking at things that you can’t see with the naked eye. Depending on the size of the thing you are trying to see, different microscopes could be used. Let’s start with the biggest things and work our way down to the smallest.
Even though cells are really small, they are one of the bigger things that can be seen with microscopes. They are big enough that you can see them with a light (or optical) microscope. A light microscope uses light and a series of lenses to magnify an object. If you use a light microscope to look at cells, you may see something like this:
To get even more magnification, you can use an electron microscope. Electron microscopes use a beam of electrons instead of light to make an image. The reason you can get more magnification with electrons is that they have much shorter wavelengths than light particles, which helps when you are trying to make an image of something. If you use an electron microscope to look at cells, you would see a lot more detail, like this:
Bacteria can be seen with either light or electron microscopes. Bacteria are much smaller than cells, thousands of bacteria can fit within a single cell! Using a light microscope, bacteria (a kind that is rod-shaped, other bacteria are more like circles) look like this:
If you use an electron microscope, you get much more magnification and so they would look like this:
Viruses are too small to see with a light microscope — they can only be seen with electron microscopes. Viruses range in size a lot: the largest is mimivirus which is as big as some bacteria but most are much much smaller than that. For the smaller viruses, hundreds of thousands of them can fit within a cell — that’s small! Here’s what an average-sized virus looks like under an electron microscope:
These are coronaviruses (my study system!) “Corona” means “crown” and they were named that because of the spikes that stick out of the virus surface — making it look like a crown.
Below is a summary to help you see what kind of microscopes you need to see different things. For atoms and smaller things, some special kinds of electron microscopes can be used to get rough images, but nothing like the pictures above!
Check out this cool site that helps you visualize how big cells, bacteria, and viruses are compared to the head of a pin!