Ricardo Diaz still remembers the night chemistry professor Joaquin Rodriguez-Lopez walked into a room full of kids and told them to throw ketchup on a volunteer wearing a special shirt. Soon the room was enveloped in ketchup, laughter, and gasps...

Microbes, human beings, and the many systems we inhabit, from farms to factories and hospitals to high schools, are all connected. Working in natural environments, research labs, and local communities, Rachel Whitaker has been...