The ozone layer is a covering of gas found high up in the stratosphere.
Lower portion of the stratosphere
15-50 km above Earth's surface
It's rich in ozone molecules, which absorb most of the Sun's harmful ultraviolet rays, preventing them from reaching the Earth.
Too much UV light can damage plants and cause sunburn in humans.
This increases the risk of cancer and premature aging of the skin.
So the ozone layer provides a protective shield for our planet, allowing complex living things, like humans, to survive.
But man-made pollution can destroy the ozone layer.
In 1985, scientists discovered a vast hole in the ozone layer over Antarctica.
BBC 'Tomorrow's World' 1987 - "Studies from space show that the hole, in blue and pink, is growing year by year, and last year spanned the whole Antarctic continent. The culprit is most probably chloro- or fluorocarbons used in aerosols and fridges."
Chlorofluorocarbons are a group of greenhouse gases commonly known as CFCs.
We used to use CFCs to make aerosols, like hairspray and paint cans.
That was until we realized that they attack the ozone layer, enabling more dangerous UV light to reach the Earth's surface.
CFCs were banned in many countries in the mid 1990s.
But ozone-depleting substances in the stratosphere can continue causing damage for 40 years after their emission.
In 2006, the hole in the ozone layer over Antarctica peaked, equalling the size of North America.
Ozone hole in 2006 = 25 million km2
By taking action to stop CFC pollution, the ozone layer is now slowly recovering.
The hole will decrease very gradually, and scientists say it could disappear within 50 years.
We learned our lesson with CFCs, and the action taken to stop their use was better late than never.
But it will be decades before the ozone layer can fully repair itself, particularly as there are links between ozone depletion and global warming.
Protecting the ozone layer is vital in keeping the Sun's harmful rays from penetrating our atmosphere and damaging the complex life beneath.