According to Chinese expert Li Xu from QuantumCTek, “absolute zero,” at approximately minus 273.15 degrees Celsius (0 Kelvin), is commonly known as the “lowest temperature in the universe.” ...

For instance, when scientists at the NIST achieved a record-setting cold temperature of 700 nK (1 nK = 10−9 K) in 1994, they used optical lattice laser equipment to adiabatically cool caesium atoms.