The key-ingredient to surface science experiments is ultra-high vacuum. This means pressures in the 10−9mbar range and below. Only such a low pressure will assure that a surface stays clean for a time long enough to do some experiments (we will see later how to obtain a clean surface). In the following, some important parts of UHV technology are described. To get a feel for it we will go down to the lab during the exercise and look at the hardware!