Lowest temperature possible

Temperature is the measure of how hot or cold something is. It is caused by how fast the atoms or molecules, that make up an object, vibrate. The coldest that any substance can theoretically be is when there is no vibration in its atoms/molecules. This is referred to as absolute zero, and it is at 0K (zero kelvin) or -273.15C. Absolute zero has never been achieved in a laboratory on Earth, and even in the coldest parts of deep space, the temperature is slightly above absolute zero. There is no upper limit to how hot something can be.