FvS: The issue of the amount of hormone that actually causes effects is very difficult for scientists to talk to people about because we're dealing with numbers that are outside of the frame of reference that anybody is going to be thinking about. We see changes, profound changes, in the course of development of essentially the whole body of experimental animals, and we're working with mice and rats, and we see these changes at fifty femtograms of the hormone per milliliter of blood. That's 0.05 trillionths of a gram of this hormone in a milliliter of blood.

DH: You've said that the doses at which hormones affect the body are extremely low. Give me an example to make me understand that.