NASA successfully deployed its James Webb Telescope in space, the agency reported.
A team of scientists had slowly been unfolding the telescope since it launched on Christmas Day.
The milestone means the device has gone a few steps further in its mission to study the universe.
NASA achieved a major breakthrough Saturday after its James Webb Telescope successfully unfolded in space, the agency announced.
The risky manoeuvre, which NASA has never pulled off before, marked the final stage of the telescope's 50 major deployments. NASA teams remotely opened the machine days after launch.
The 21-foot instrument was blasted into the skies from French Guiana on Christmas Day. Astronomers expect Webb to fill a mysterious gap in the historical record of our universe - the first 400 million years after the Big Bang - and identify distant worlds that could host life.
NASA Administrator Bill Nelson said in a press release: "Today, NASA achieved another engineering milestone decades in the making. While the journey is not complete, I join the Webb team in breathing a little easier and imagining the future breakthroughs bound to inspire the world."
He added: "The James Webb Space Telescope is an unprecedented mission that is on the precipice of seeing the light from the first galaxies and discovering the mysteries of our universe."
The telescope, which is 100 times more powerful than its predecessor, the Hubble Space Telescope, cost $10 billion to create and was developed in conjunction with the European Space Agency and Canadian Space Agency.
The unfurling of Webb was a tricky proposition. Webb has two major components: a hexagonal mirror made of 18 gold-coated segments and a sunshield the size of a tennis court, which deflects sunlight to keep the telescope cool. Both were too large to fit in a rocket, so NASA folded them up like a drop-leaf table.
The successful completion means the telescope will spend about four months aligning and focusing its mirrors. Then the observatory will calibrate its science instruments: four cameras and spectrographs designed to observe the universe in different wavelengths of infrared light.