What's the principle of fractional distillation?

The main steps involved in fractional distillation are:

1. Heating: The mixture of miscible liquids is heated in a distilling flask that has a fractionating column connected to its tip. 
2. Evaporation: As the mixture heats up, the substance with the lowest boiling point vaporizes first. This forms a vapor that rises into the fractionating column.
3. Condensation: As the vapor rises through the fractionating column, it cools down. When it reaches a height where the temperature is lower than its boiling point, it condenses back into liquid form.
4. Collection: The condensed liquid is collected in different compartments of the fractionating column or in separate collection vessels. Each compartment or vessel contains a fraction that is rich in one of the components of the mixture.
5. The temperature is gradually increased, causing substances with higher boiling points to vaporize and condense at different levels in the fractionating column. This separation process is repeated until all desired fractions are collected.