Look at this black and white image. There's something hidden.
If you can only see zigzagged white and black lines, take a few steps back from the screen, or turn it to a near 90 degree angle.
If you were wondering what it was, it's the logo, featuring a giant panda, of the World Wide Fund for Nature (WWF).
If you are wondering where the panda was hidden, it was roughly here (look again):
It was uploaded to Imgur three years ago and its popularity has risen from time to time on the internet due to the optical illusion which alludes to the conservation efforts towards giant pandas.
The WWF say that the latest panda census in 2014 found that there were 1,864 alive in the wild, with numbers having risen from around 1,000 in the late 1970s. They are currently listed as endangered on the IUCN red list.