The top of a 3,000m-high (10,000ft) mountain in Chile has been blown up to make way for the world's largest optical and infrared telescope.
A million tonnes of rock were blasted in order to create a level surface on which to build the European-Extremely Large Telescope (E-ELT).
At its heart will lie a mirror that is half the size of a football pitch.
This will allow astronomers to look further into space and in more detail than ever before.
The explosion in Cerro Armazones in northern Chile took place just after 1840 BST and was streamed live by the European Southern Observatory.
Dr Aprajita Verma, deputy project scientist for the E-ELT's UK team at the University of Oxford, said: "The telescope is a really huge step in terms of its scale - it's so much bigger than anything else.
"It will give us a deeper and finer view of the Universe."
Now the mountaintop has been levelled, the construction of the E-ELT will begin. It is expected to take less than 10 years.
The site, in the middle of the Atacama desert - and close to the Very Large Telescope - has been chosen because of its near-perfect observing conditions: for most of the year, the sky is cloudless.
The aridity there also means there is little water vapour to cloud its view of space.
One of the most challenging aspects will be to create and install the telescope's 39m-wide (130ft) primary mirror.
This will be made from 798 smaller hexagonal mirrors, each 1.4m-wide (4.6ft) and less than 50mm (2in) thick. Prototypes are currently being created by OpTIC Glyndwr Ltd, which is linked to Glyndwr University in Wales.
This technology will allow the telescope to capture 15 times more light than any other optical telescope and it will create images that are 16 times sharper than even the Hubble Space Telescope, which orbits high above the Earth.
Dr Verma said: "This telescope will be so powerful that it will collect enough light to look to the observable limit of the Universe - soon after the Big Bang when the first stars and galaxies formed.
"We'll be able to see when the Universe switched on."
She said that it could also provide a detailed view of exoplanets - other worlds outside of the Solar System.
"Well be able to look at the planets directly, look at their atmosphere and potentially look for signs of life," Dr Verma added.
The European Southern Observatory, which is building the telescope, has 15 member states, including the UK.
The project will cost more than a billion euros.
How the European Extremely Large Telescope (E-ELT) will work
- 39.3m-wide primary mirror (M1) is made up of almost 800 segments
- M2 is 4.2m wide and hangs upside down. It will weigh less than 12t
- 3.8m-wide M3 sits in a hole in M1. M3 moves with M2 and M4 to focus
- 2.4m-wide M4 can deform its shape to remove twinkling in stars
- M5 is 2.6m x 2.1m. It stabilises the light on to the instrument detectors
- Lasers make artificial stars on the sky to help correct the imaging
- E-ELT will have two instrument decks; each deck to hold three units
- The telescope will be sensitive to visible and near-infrared light