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Millions of years into the future, humans may not exist anymore.

It might seem like a scary thought, but it's not something we need to worry about.

Lots of species go extinct over time, and it's only natural that one day it could happen to humans too.

If, just like the dinosaurs, humans are history - scientists now think they've found a way to bring us back.

They've printed the blueprint for what makes a human, called a genome, on something called a '5D memory crystal'.

The hope is that at some point in the future someone or something - yes, that could be aliens - will find it and make new humans using the information stored inside.

A team at the University of Southampton was led by Professor Peter Kazansky.

He told 91�ȱ� Newsround how it all works: “These memory crystals, around the size of a coin in your hand, can store huge amounts of information.

"What’s amazing about these crystals is that they can last a really long time, billions of years, without being damaged or losing the information inside them. It’s like having a memory that can never be forgotten.

“On this particular crystal, we’ve stored the entire human genome - all the instructions that make us who we are.

"That means some future civilisation (or even aliens!) could discover the crystals and use them to learn all about us, long after we’re gone. It’s like the ultimate time capsule for important knowledge.”

The team have called it 5D as it can show the genome from two angles and in three dimensions.

This is better than printing something on a flat piece of paper as future lifeforms will be able to see what it looks like as a physical object.

The crystal can last for billions of years without breaking down - in fact, it holds the Guinness World Record (awarded in 2014) for the most durable data storage material.

The material can survive being frozen, put in a fire, and even in temperatures of 1000 degrees.

The team at the University of Southampton think that, if found by another life form in the future, it will preserve the information well enough for them to use it and bring humans back to life.

That being said, it's not currently possible to make a human synthetically - in other words, by any other process than being born.

The crystal is stored in the Memory of Mankind archive – a special time capsule within a salt cave in Hallstatt, Austria.

There is a key engraved on it for whoever may find it in the future.

“The visual key inscribed on the crystal gives the finder knowledge of what data is stored inside and how it could be used,” Prof Kazansky explained.