If it's mid-May in New York City, you can be sure that pollen will be plentiful. To learn more about what's behind all our watery eyes and sneezing, we sat down with Guy Robinson, a senior lecturer of natural sciences.

Robinson runs the Fordham Pollen Index, which is based on pollen collected from the air at the Lincoln Center campus and the Louis Calder Biological Field Station in Armonk, NY.