"The cooled copper mass...was the coldest cubic meter in the universe for over 15 days," the Institute (INFN) said on its website.
"It is the first experiment ever to cool a mass and a volume of this size to a temperature this close to absolute zero [0 Kelvin]," it said.
The cubic meter, or 35 cubic feet, of copper weighing 400 kilogrammes was brought to a temperature of six milliKelvins or minus 273.144 Celsius.
Absolute zero - considered the lowest possible temperature - is -273.15C or zero on the Kelvin scale, named after 19th-century Irish engineer and physicist William Thomson, 1st Baron Kelvin, credited with establishing the correct value of the temperature.
The feat was accomplished at the Cryogenic Underground Observatory for Rare Events (Cuore), a particle physics laboratory in central Italy gathering scientists from Italy, the United States, China, Spain and France.
The copper was enclosed in a container called a cryostat, "the only one of its kind in the world, not only in terms of its dimensions, extreme temperatures and cooling power, but also for the...very low levels of radioactivity," INFN said.
"No experiment on Earth has ever cooled a similar mass or volume to temperatures this low; similar conditions are also not expected to arise in Nature," it said.
Cuore is located at Italy's Gran Sasso mountain, the highest peak in the Apennines some 120 kilometres from Rome.