Central Asia's inhabitants are largely descended from nomadic tribes who have lived under powers ranging from Alexander the Great and Mongol leaders to Soviet communists.
Each Central Asian nation has its own indigenous population.
All these are mainly sunni Muslim and speak languages with similar Turkic roots - apart from the Tajiks whose language is similar to the Iranian language Farsi.
Kazakhstan is the most ethnically mixed.
Under Soviet rule, natives became outnumbered by an influx of Russians, Ukrainians and Germans, although many of the immigrants have now left.
Turkmenistan is the most ethnically homogeneous - indigenous Turkmen account for 85% of the population.
Uzbeks are most widespread, forming the second largest population group in Tajikistan, Kyrgyzstan and Turkmenistan.
Central Asia is also home to minorities including the Karakalpaks in Uzbekistan and Uighurs - Turkic Muslims concentrated mainly in Western China.
The region's inhabitants cluster most densely in the lush valleys of Uzbekistan and Tajikistan, and populate crumbling Soviet-built industrial cities.