Desalination is the process of removing salt from seawater to make it drinkable. Since 97% of Earth's water is salty ocean water, desalination lets coastal cities and dry regions turn abundant seawater into fresh water people can actually use.

One common method works like a giant teakettle: seawater is heated until it evaporates into steam, leaving the salt behind. When the steam cools back into water, it's fresh and clean. Another method forces seawater through special filters so tiny that water molecules squeeze through but salt particles can't. Both processes require substantial energy, which makes desalinated water more expensive than water from rivers or wells.

Countries like Saudi Arabia and Israel rely heavily on desalination because they have limited rainfall but plenty of coastline. California has built desalination plants to help during droughts. As technology improves and costs decrease, desalination becomes more practical for places struggling with water shortages. Scientists are working on making desalination cheaper and more energy-efficient, since access to clean drinking water remains one of humanity's most critical challenges.