When the first pit holding the Terracotta Warriors was opened up after their chance discovery in 1974, in addition to the troops, archaeologists found horses and the remains of wooden war chariots.
Two years later, a second pit was unearthed; it contained over a thousand warriors and the remains of 90 war chariots. The same year a third pit was located: it appeared to be the command centre of the armed forces and included 68 warriors, four horses and the rotted remains of another war chariot.
A close-up of the charioteer on the chariot that is on show at the exhibition. This is how he started life - as bright, shiny, bronze, which was then gradually aged to look just as he does today.
These discoveries made clear that chariots and warriors were the principle fighting forces in the Qin Dynasty.
But apart from the four terracotta horses that drew each unit, only the outlines of the chariots, plus their bronze fittings, were left. The wooden chariots had rotted away long ago - so that today when you gaze out at the first pit, you see columns of soldiers, followed by horses standing in front of small mounds of rubble C what used to be the war chariots.
In 1978, exploration began of an area only 20 meters or so east of Emperor Qin's mausoleum - about one and a half kilometres from the three pits containing the wooden war chariots and the warriors.
Experimental drilling turned up some bronze and gold, and small pieces of what seemed to be a horses harness. Two years later, in 1980, excavations revealed more horses and chariots in this new pit, about eight meters below the earths surface.
But this time the two chariots the archaeologists uncovered were made not of wood, but of bronze - and so were the four horses pulling each of them, and the charioteers driving them.
They were half life-size, faithfully copied down to the last detail, and had been contained in a 6.8 metre wooden coffin that had rotted away. The bodies of the horses were still reasonably intact, but their legs and the chariots had been crushed by the weight of the earth on top of them.
The question was: Were these chariots, too, part of the Qin army?
It was quickly determined that they were not. Both the wooden and the bronze conveyances were horse-drawn chariots, but their purposes are totally different.
The war chariots in the three pits nearly a mile away were part of the military machine. But the bronze chariots buried quite close to the Emperors tomb have nothing to do with war or the warriors:
They are, in fact, almost certainly for the Emperor to tour his realm in the afterlife C just as he had carried out inspections in a full-size version of one of the chariots in real life.
The interior of the bronze chariot in the exhibition after its aging had begun. Even though they are unseen, the roof is ribbed and the walls and window are meticulously painted even inside - just as the original.
When the two chariots were finally dug out, they were lined up one behind the other and all the pieces seemed to be there --- but there were about 3,000 bits and pieces
They couldnt be restored in the pit, so a platform was placed under them and eight tonnes of chariot metal was moved to a workshop where the jigsaw could be re-assembled.
Researchers say that construction of the chariots involved different techniques, such as casting, riveting, welding, embedding, mounting and carving, and a team of 30 craftsmen laboured for eight years to restore these treasures.
They are remarkable works of art, with meticulous detail even in areas that cant be seen. For example, the bits inside the horses mouths have sharp points that the driver can use his reins to pull on to a horses tongue if it ever bolts.
Chariot one is 2.25 metres long and is known as the high or inspection chariot. Its purpose seems to have been to guard and clear the way for the chariot following. There is a large umbrella to provide shade for the driver.
Chariot two is larger (3. 17 metres long; 1.29 m wide) than the lead chariot and is even more wonderful than the first C because it is for the Emperor. It weighs over 1200 kilograms.
The charioteer (sitting back on his heels) drives, and the compartment behind him is occupied by Qin Shihuang Di. It is referred to as the comfort (or comfortable) chariot: the walls are decorated with geometric and cloud patterns; there are three windows - one in the front, one on each side of the compartment - and a door that opens at the rear.
The roof is shaped like a turtles shell (which symbolises longevity) and is also said to be symbolic of the round sky. The horses are richly adorned with gold and silver.
The chariot from the Emperors tomb will never be allowed out of China. If you cant make it to Xian or (for the next three months only) to the British Museum, this is your chance to see one of the worlds great works of bronze art.
A collection of some of the hundreds of hand-made fittings that adorn the horses and the chariot.
This is exactly the same bronze charioteer shown above only now he has lost his glow and aged 2,200 years especially for the Terracotta Warriors of Qin exhibition.
850,000 Saw Warriors at the British Museum 
2009