Here's a short story:

Tibet (i/tᵻˈbɛt/; Wylie: Bod, pronounced [pʰø̀ʔ]; Chinese: 西藏; pinyin: Xīzàng) is a region on the Tibetan Plateau in Asia. It is the traditional homeland of the Tibetan people as well as some other ethnic groups such as Monpa, Qiang and Lhoba peoples and is now also inhabited by considerable numbers of Han Chinese and Hui people. Tibet is the highest region on Earth, with an average elevation of 4,900 metres (16,000 ft). The highest elevation in Tibet is Mount Everest, earth's highest mountain rising 8,848 m (29,029 ft) above sea level. 

The Tibetan Empire emerged in the 7th century, but with the fall of the empire the region soon divided into a variety of territories. The bulk of western and central Tibet (Ü-Tsang) was often at least nominally unified under a series of Tibetan governments in Lhasa, Shigatse, or nearby locations; these governments were at various times under Mongol and Chinese overlordship. The eastern regions of Kham and Amdo often maintained a more decentralized indigenous political structure, being divided among a number of small principalities and tribal groups, while also often falling more directly under Chinese rule after the Battle of Chamdo; most of this area was eventually incorporated into the Chinese provinces of Sichuan and Qinghai. The current borders of Tibet were generally established in the 18th century. (End of story)

Provide your best guess for the following question. Give ONLY the guess, no other words or explanation.

For example:

Guess: <most likely guess, as short as possible; not a complete sentence, just the guess!>

Here are a few examples of questions and answers:

Question: When were the current borders of Tibet established?
Guess: 18th century

Question: What is the average elevation of Tibet?
Guess: 4,900 metres

Question: What is earth's highest mountain?
Guess: Mount Everest

Question: When did the Tibetan Empire emerge?
Guess: 7th century

Question: Where is the region of Tibet located?
Guess: 8,848 m (29,029 ft) above sea leve

Question: What plateau is it on?
Guess: Asia

Question: Besides the Tibetan people what other groups are there in Tibet?
Guess: Monpa, Qiang and Lhoba

Question: What is the highest region on earth?
Guess: Tibet

Question: What eastern regions  maintained a more decentralized structure?
Guess: f Kham and Amdo

Now answer the following question in the same format.

Question: What happened to the Tibetan Empire with it's fall?

fell under Chinese rule