When I was in graduate school in the early 80's I wanted to get a PhD in toxicology (but didn't, became a programmer instead). Today if I was at that same stage

When I was in graduate school in the early 80's I wanted to get a PhD in toxicology (but didn't, became a programmer instead). Today if I was at that same stage I would study the microbiome, it's a fascinating melange of chemistry, microbiology and food science, and we still know very little about it, plus it can make a huge difference in the world. Toxicology seemed too much like slaughtering rats for a living.