India, Jan. 2 -- It's like a giant ocean above our heads. It holds, like the oceans, a host of unanswered questions.

Among the ones that concern us most directly: What happens to what's in the air we breathe? How much gets into the bloodstream; what impact does it have?

Zooming out, more queries take shape: In what ways can the tiniest particles in the air affect monsoon patterns, or intensify storms? How do these aerosols affect disease transmission?

Lidia Morawska, 73, a Polish-Australian aerosol scientist, has been researching some of these questions for 35 years. Her area of focus is a particularly invasive component: ultrafine particles (UFP; smaller than the smallest particulate matter of 2.5 microns captured by air-quality monit...