Mexican President Vicente Fox has inaugurated a giant telescope that could help scientists uncover clues about the origins of the Universe.
The telescope has been built on the summit of an extinct volcano
The telescope, which resembles a gigantic satellite dish, sits high in the mountains of central Puebla state.
It will pick up radio waves that have been travelling through space for some 13 billion years.
The telescope's antenna has a diameter of 50m (164ft) and is the largest of its kind in the world.
"This telescope will allow us to make fundamental discoveries about the formation and evolution of galaxies, about the formation and evolution of stars, and about the origin of the Universe itself," National Astrophysics Institute Director Jose Guichard said during the inauguration.
Scientists say it is the most important scientific and technological project in the country's history.
The Large Millimeter Telescope (LMT), which cost $120m, was partly funded by the US. As its name suggests, it will be sensitive to electromagnetic radiation at millimetric wavelengths - about 0.85mm to 4mm.
This will give it the ability to see through the dust in the interstellar medium that obscures the view of many other astronomical facilities.
President Fox said it would "put Mexico in the scientific and investigative vanguard in this field".
The telescope is built on the 4,580m (15,026ft) summit of an extinct volcano called Sierra Negra - the fifth highest peak in Mexico.
The air on the peak is so thin that scientists working at the site have to have bottled oxygen to hand in case they faint.