R oots provide plants with mechanical stability and pure water. Wind and gravitational forces on plants are spread out by the roots over a large volume of soil. In a similar manner, roots absorb pure water and nutrients from moist soil. These processes are mathematically similar and have similar optimal solutions, unless the soil is inhomogeneous-i.e., if one part is wetter, whereas another part provides more of a grip for the roots to hold onto. A root system with a given weight has an optimal shape if it quickly produces large amounts of clean water at a low energy cost. By understanding the optimal shape of roots we may be able to exploit this natural structure to improve water desalination systems.Access to water is a prerequisite for life, including human life, not only as drinking water but also for agriculture and industry. According to the World Health Organization, over 1 billion people in the world lack adequate clean water and about 43% of the Earth's human population live in water scarce areas, while the population grows at over 80 million per year [1]. As the demand for freshwater increases and the quality of existing supplies deteriorates, the need for efficient techniques for fresh water production increases. Over 97.5% of the Earth's available water resources are contained in seawater or saline aquifers [2]. Although desalination solutions have not yet attained the level of widespread acceptance which their economic potential suggests they could, at present 40 million m 3 of potable water is produced per day by some 150,000 desalination facilities throughout the world [3]. Most desalination is done by reverse osmosis, although thermal distillation, which is roughly 10 times as costly in energy, is also prevalent. In reverse osmosis systems a semi-permeable polymeric membrane separates a freshwater tank from a high pressure saltwater tank. If the pressure difference exceeds the osmotic pressure, water flows through the membrane from the fresh water tank and leaves the salts behind in the salt water tank.While the idea behind reverse osmosis is simple, the implementation can be challenging. Current research seeks to improve the performance of the membranes, possibly with biological water channels known as protein aquaporins [4], and molecular dynamics designs of carbon nanotube membranes for efficient desalination [5,6]. Other recent studies elucidated the nature of pore-ion interactions under osmotic processes. They concluded that osmotic flux through negatively charged pores is higher than for positive charged pores [7][8][9][10][11].However, even with an ideal membrane, which lets water pass easily and blocks all salt, conventional reverse osmosis systems are inherently inefficient for the following reason: As water passes through the membrane salt is deposited on the membrane and has to be moved away, against the flow of the water. If desalination is done at a reasonable rate, this leads to a very high salt concentration near the membrane compared with the rest of the salt reservoir. Osmotic pr...