The most famous of all the stones, which measure less than eight centimetres across and are made from a variety of different materials including granite and sandstone, is the Towie Stone, found in Aberdeenshire.
Historians believe it dates from between 1500BC - 3500BC.
The original purpose of the stones, which have also been found in Ireland and northern England, has left experts baffled.
The stones are carved with a number of small knobs or bosses on the surface, ranging from three to 10. Most of the balls discovered have six protruding bosses although one found in Kincardineshire in 1890 had 14 bosses.
The stones are also engraved with patterns that could relate to ‘Platonic solids’, the polyhedrons thought by ancient Greek mathematician and philosopher Plato to form the classical elements of earth, water, air, fire and ether.
But the stones found in Scotland were made long before Plato recorded his hypothesis in the Timaeus, close to 2000 years prior.
One architect has suggested that the 5,000-year-old stones might have formed a sort of ‘Rubik’s Cube’ for use in construction and building, after one was found underneath the buttress of a late Neolithic structure unearthed at the Ness of Brodgar, on Orkney.
Some mathmeticians believe that the carved stones may have been used in early geometrical experiments.
But the true use for these spheres remains unknown.
There have been many different theories offered up as possible explanations for the stones. Some think they could have been used as weapons, other theories focus on the stones being used as weights in fishing nets while a ceremonious use in certain rituals is another suggestion.
Another theory is that the stones were used to signify power and authority.
But none of the alternative theories stuck, and so the actual function of the stones is still unknown.