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Have you ever wondered why wee is yellow? Has it puzzled you for a long time, or are you curious to find out? Scientists now think they have the answer.

It's all to do with our gut, and how we break down cells.

We already knew that the yellow comes from a substance called urobilin, but now scientists know why that substance is made in the first place.

Time to solve that myster-wee with a science lesson...

Why is our wee yellow?

The yellow colour in our wee, or urine, is there because of a special substance called urobilin.

Urobilin is made when blood cells break down, making an orange substance called bilirubin. This goes into your gut, and after some impressive biological processes, becomes another substance.

This new substance has a big scientific word - it's called urobilinogen. Try saying that quickly.

Thanks to the processes in your body, this turns into urobilin - making the wee yellow.

Your wee travels out of your kidneys, is stored inside your bladder, and then when you go for a wee it is pushed out and ends up in the toilet.

Up in space, once the wee comes out, that isn't the last you'll see of it. On board the ISS, they recycle their wee, using it (alongside sweat and breath) for water.

Using science, they turn it back into perfectly drinkable water. You can read about it here.