How can crude oil be separated into different fractions?

Crude oil is a mixture of different hydrocarbons, of varying length. As they have different boiling points they can be separated.Crude oil is heated/vaporised from oil to gas.These vapours enter the fractionating column, which is hotter at the bottom and gets cooler at the top (there is a temperature gradient).The vapours then condense (go from gas to liquid) at different levels when they reach their boiling points.