If sufficient pressure, about 20 times that of the domestic water supply system, is applied to a salt solution that is separated by an osmotic membrane from fresh water, water is driven from the solution into the fresh water. Membranes available until 50 years ago permitted little water to permeate, and therefore the process was uneconomic. At UCLA in 1959, Sidney Loeb and Srinivasa Sourirajan invented the Loeb-Sourirajan membrane that separated the salt, withstood the pressure and allowed sufficient water to permeate. This breakthrough made reverse osmosis (RO) desalination practical. Dr. Loeb then built the world's first RO desalination plant in Coalinga, California. In 1967, the Negev Institute for Arid Zone Research in Beersheba, with the help of UNESCO, invited Prof. Loeb to Israel for three months, where research and application continued. Under his supervision a membrane production facility was constructed in Beersheba and a 150 cubic-meter-per-day experimental plant built at Yotvata to desalinate water with a salinity a 10th that of sea water, pumped up from under the Negev desert. Operation of the Yotvata and subsequent prototype plants gave valuable experience for the development of desalination in Israel. Prof. Loeb stayed on in Israel, and when the Institute was incorporated into Ben-Gurion University, joined its department of chemical engineering, where he continued his teaching and research. His knowledge was further diffused into the technical community in Israel by courses he gave to the Mekorot national water company and at the university, and by associates and students who went on to work for organizations active in the field of desalination. Prof. Loeb became Israeli in many ways. In May 1967, although advised by the US authorities to leave, he stayed on, saying to friends, "I cannot leave my country." During the Yom Kippur War he volunteered to use his car to transport entertainers in Sinai, where along the way he picked up a hitchhiker - a thirsty, surrendering Egyptian commando. In desalination, energy goes in and fresh water comes out. In anticipation of the proposed Med-Dead canal, Prof. Loeb proposed the pressure-retarded osmosis (PRO) process to create usable energy from the meeting across a membrane of more and less salty water. He was awarded a PRO patent in 1975. This is now being developed world-wide, notably in Norway, to generate clean energy at locations where fresh water meets salty water. Sidney Loeb was much respected and recognized internationally and received numerous awards. The European Desalination Society established a biennial award for innovation in his name. The RO industry he pioneered has become a multi-billion dollar business. Installed RO plants, including Ashkelon and other Israeli facilities, are currently at 13.5 billion cubic meters per year - around 60 percent of the total world-wide desalination capacity and growing, with another 17,000 small industrial, household and ship-mounted RO systems in use. An imaginative and daring inventor, Prof. Loeb was a man of exceptional honesty, integrity, modesty and loyalty to his friends. Friends and neighbors knew him as a man of entertaining humor, a tennis player, a peace supporter and the moving spirit in the local English-language book club. Prof. Loeb was predeceased by a son, David, who perished in a mid-air airplane collision in California, and is survived by his devoted wife of 38 years, Mickey (Miriam), neÃ© Rosenberg. The world population today is close to 7 billion people, headed for around 10 billion by 2060. Desalting of both natural and recycled water is becoming essential for many of those billions. Prof. Loeb enjoyed the satisfaction of knowing that he had contributed so much to the welfare of so many, now and in generations to come.