(e.g. the migration of liquid through a semi-permeable partition (e.g. clay or parchment paper or cell walls in living organisms), which separates two liquids of different concentrations. Osmosis also plays an important role in metabolism. The Danish chemist Jacobus Hoff (1852-1911) discovered the phenomenon in 1874. This partition (also known as a diaphragm) is permeable only to the molecules of a liquid (e.g. water), but not to the dissolved substance (e.g. sugar molecules), thanks to a corresponding pore size. A diffusion (flowing apart) takes place towards the concentrated solution. If a container-1 (with a semi-permeable outer wall) with a highly concentrated solution (e.g. sugar water) is placed in a container-2 with pure water in such a way that the liquid level in both containers is the same, the water molecules migrate towards container-1.