I am amazed by epigenetics, which is the study of gene changes caused by our lifestyle/experiences. I am especially intrigued by changes that affect the so-called germ line, meaning they are can be inherited by the next generation. Yes, if you are remembering, from high school bio, that guy Lamark who said giraffes got tall necks because they stretched them and passed on their efforts to their kids? The one everyone laughed at? Well, he is getting his props now. Apparently, natural selection isn't the only thing at work on a population's genome.
Two fun epigenetic facts:
The tobacco habit of a grandparent or great grandparent could be the cause for your kid's allergy -- even if they have never met.
Curing your kids allergies could prevent your grandkids from ever being allergic or asthmatic in the first place.