Sure, you look human on the outside, but that’s just your shell. Inside, the real operation is run by “about 100 trillion bacterial cells. They outnumber human cells 10 to one and account for 99.9 percent of the unique genes in the body.” At the risk of getting too esoteric, these bacteria are the Oompa Loompas in your internal candy factory. And certain modern human behaviors, such as popping antibiotics like Tic Tacs, might be dramatically altering our microbiome. The NYT’s Jane E. Brody explains the problem: “Like ecosystems the world over, the human microbiome is losing its diversity, to the potential detriment of the health of those it inhabits.”

+ Gut Reaction: How what you eat can amp up or tamp down stress.