Sea spray aerosol is generated from breaking waves and constitutes a major source of aerosol particles to the atmosphere.  Sea spray aerosol affect climate directly via interaction with light and indirectly via their influence on cloud formation, cloud lifetime and radiative properties.  Sea spray aerosol span a wide size range and are complex particles which may contain inorganic salts as well as organic molecules and biological material. This talk addresses the properties of sea spray aerosol with special focus on volatility and ability to form cloud droplets. Results from laboratory experiments using artificial as well as real seawater samples will be presented and discussed.