Which central asian republic extends into eastern europe?

The correct answer is - Kazakhstan.

The country of Kazakhstan, that officially falls under the Central Asian region, has a small part that enters the territory of Eastern Europe, with its part that occupies the plain north of the Caspian Sea/Lake. This country is one of the top 10 largest in the world. It is a country that is populated mostly by Kazakhs (one of the Turkic people) and Russians, where the Kazakh and Russian language are the two official languages. The country is well known for the nuclear testings that took place in its northern part, and also for the launching of space shuttles and satellites into the space.