How did the Universe originate and what is it made of?

To understand the nature of dark energy and dark matter by accurate measurement of the accelerated expansion of the Universe through different independent methods.

Galaxies and clusters of galaxies out to z~2,
in a wide extragalactic survey covering 15 000 deg², plus a deep survey covering an area of 40 deg² 

Mission home: http://sci.esa.int/euclid