Imbibition is a special type of diffusion when water is absorbed by solids-colloids-causing them to enormously increase in volume. The classical examples of imbibition are absorption of water by seeds and dry wood. The pressure that is produced by swelling of wood had been used by the prehistoric man to split rocks and boulders. If it were not for the pressure due to imbibition, seedlings would not have been able to emerge out of soil into the open; they probably would not have been able to establish.