WILL: Welcome to the NeuroTrailblazers Podcast. I'm Will.

JULIAN: And I'm Julian. I'm six and a half. Dad, how does a piece of brain turn into one of those colorful maps?

WILL: Let's walk through it. We'll follow the microscope method in the Neuronauts story. First we prepare a small piece of brain tissue so we can study its tiny parts.

JULIAN: Are you taking pictures inside somebody's head?

WILL: For this method, no. The tissue has been removed and is no longer living. This is different from the kind of brain scan a person might have at a hospital.

JULIAN: Okay. What do you do with the little piece?

WILL: Special chemicals help keep its shape. Other chemicals make the edges of the cells easier to see. Then we put it in a firm material that holds it steady.

JULIAN: Why do you need to see the edges?

WILL: So we can tell which part belongs to which cell. Imagine trying to color a picture when you can't see the lines. You might accidentally color two different things as one.

JULIAN: I have done that. So now the lines are easier to see. What's next?

WILL: We need to see inside. One way is to cut the piece into very thin slices, much thinner than a hair. A special cutting tool can have a diamond edge.

JULIAN: A real diamond? That's a fancy little knife.

WILL: A very sharp one. The slices must stay in order. Some methods keep the slices, and others remove one thin layer at a time as they take pictures.

JULIAN: Why does the order matter so much?

WILL: Think about a loaf of raisin bread. Look at the slices one by one, in order. The pictures help you work out where things were inside the whole loaf.

JULIAN: But we're looking for cell branches instead of raisins. And we can't mix up the slices.

WILL: Exactly. A powerful microscope takes the pictures. It's called an electron microscope. It can show tiny details that an ordinary camera can't see.

JULIAN: My phone can zoom in. Could I just keep zooming?

WILL: Zooming makes what's already in a picture bigger. It can't bring back a detail the camera never captured. We need a tool that can see those details in the first place.

JULIAN: Okay. Special pictures. Lots of slices. Are we at the map yet?

WILL: Almost, but there are a few important steps left. First, a computer lines the pictures up. A slice may have moved or bent a little, so matching the pictures takes care.

JULIAN: Like straightening a stack of papers so the corners line up.

WILL: That's the idea. Then we follow each cell from one picture to the next. Computers help label which pieces belong together. Each cell can get its own color on the screen.

JULIAN: Oh, so the cells aren't really purple and bright green?

WILL: Those colors are added to help us see the map. We also look for the tiny places where cells connect. Following the branches tells us where they go. Finding connections tells us who connects to whom.

JULIAN: Can the computer get those paths wrong?

WILL: Yes. It might join two different cells together. Or it might lose track of a branch and leave part out. People check the map against the original pictures and fix mistakes.

JULIAN: Like when I check my writing and find a word I missed.

WILL: Right. This checking is called proofreading. Here you're checking cell shapes and connections. If you're unsure, you look more closely or ask someone else to help.

JULIAN: Then what do you do with the checked map?

WILL: Use it to ask questions. For example, which cells connect to a group that helps an animal see movement? The map gives us clues we can test with other experiments.

JULIAN: So the point isn't just to make a really big, colorful picture.

WILL: Exactly. The point is to learn something. Let's pause and see how much you remember. What comes before we can follow the paths?

JULIAN: Prepare the little piece. Make thin layers. Take pictures. Put the pictures in order. Then follow the cells and check their connections.

WILL: You've got the journey. No need to remember every tool's name. And every step has people helping it work. Next time, we'll talk about ways you can get involved.

JULIAN: Even if you're still learning. Find the story at NeuroTrailblazers dot org. See you next time!