Oil refinery. Atmospheric pipestill (right) and a vacuum pipestill (left). These are distillation towers (stills) where hot crude oil is separated into parts called fractions. The crude oil, a mix of hydrocarbons, is heated to around 400 degrees Celsius and piped into the base of the atmospheric pipestill. Hydrocarbon gases from the boiling oil rise up the tower towards the coolest area at the top. The fractions are collected at different levels, depending on their boiling points. Ones with a low boiling point (petroleum gases, petrol) rise towards the top of the tower. Ones with a higher boiling point (jet fuel, diesel) condense lower down. The part that doesn't boil is sent to the vacuum pipestill, where vacuum boiling yields parts such as fuel oil and bitumen. Photographed at ExxonMobil's Fawley Oil Refinery, Hampshire, UK.