The best thing to do when you get home from work is to relax and heal your mind. There are many different ways to exercise the brain, but my favorite are brainteasers for keeping the brain sharp.  My favorite brainteasers of late are about finding a specific detail in a picture.

These kinds of tests are called optical illusions, or picture puzzles, and have been around forever, but it’s only recently that I started doing them regularly. To solve them, you must find a certain pattern, object or something else that stands out in a particular photo.

To find small details, it‘s extremely important to focus all your senses — you need to concentrate to the maximum.

You only have 15 seconds (for a more interesting challenge). This adds fun and lets you develop your competitive instinct.

Here is the picture, the challenge lies in finding a face among the stones in the picture. Can you solve it?

It’s clever, but it makes you struggle! Did you find it? If not, the answer will be obvious below.

There’s the face, camouflaged in the rocks!

Do you see the hidden woman?

Okay, there’s one more and this one is even trickier than the first one, so now you really need to focus. Remember, you only get 15 seconds — in the next picture, can you find the hidden woman?

Did you spot her? She is very tactful when it comes to blending with the background. If you can’t see her, check the answer below.

There! You can just barely see her leg and knee. This was really difficult so congratulations if you found it on your own.