Aerosols are rarely talked about, yet they're having a significant effect on the quality of the air we breathe. These particles are typically a thousand times smaller than the width of a hair, and they come from a variety of sources, such as car exhaust and factories, as well as volcanoes and wildfires. The ocean also contributes to the story, with viruses, bacteria, phytoplankton and enzymes present in sea air. In addition, dust particles from Asia find their way to the shores of the United States. Airborne particles such as these can negatively affect the upper respiratory tract, and recent research indicates that they can affect our brain. Vicki Grassian is an Associate Dean in the Division of Physical Sciences at UC San Diego and a Distinguished Professor with appointments in the Departments of Chemistry & Biochemistry, Nanoengineering and Scripps Institution of Oceanography. Her research includes environmental and atmospheric chemistry, especially as it relates to atmospheric aerosols, environmental interfaces, and environmental and health aspects of nanoscience and nanotechnology. This talk was given at a TEDx event using the TED conference format but independently organized by a local community. Learn more at www.ted.com/tedx