If you enjoy challenging yourself, this is the perfect brainteaser for you.

In this optical illusion, there are 10 faces – how long does it take you to find them all?

Those who look closely may notice that they recognize some or all of the faces.

This is because the illusion is called the National Leaders Tree featuring former leaders including former British Prime Minister Margaret Thatcher and ex-Soviet leader Mikhail Gorbachev.

The higher up the tree you go, the harder the illusion becomes.

All of the faces are created by the way the tree branches bend and grow off each other.

If you are struggling to find all 10 faces, take each main branch of the tree one at a time.

First, look up at each branch on the left-hand side of the tree and then do the same on the right side.

Some of the heads of the leaders merge into others so make sure you look carefully when you find one of the many faces.

For those who give up, scroll down to reveal where the faces are.

If you enjoyed that challenge, why not try this real-life illusion?

See if you have what it takes to survive in the wild.

The winter scene depicts an icy waterfall and rugged, rocky terrain covered in a fresh coat of snow.

The scene almost appears entirely in black and white with the gray rocks contrasting with their snowy cover.

Images of animals in the wild can often be fantastic illusions due to their ability to camouflage themselves in their natural habitats.

Scroll down to reveal where the polar bear is – you might be shocked to see that he is looking right at you.