Image of cultured bacteria in a petri dish

Typical gut bacteria grown in a petri dish • Image by Nicola Fawcett and Christopher Wood (CC BY-SA 4.0)

Illustration of bacterium

Staphylococcus bacteria • Image by Scientific Animations (CC BY-SA 4.0)

Microscopic image of E. coli bacteria

E. coli bacteria • Photo by Janice Haney Carr, National Escherichia, Shigella, Vibrio Reference Unit at CDC, USCDCP on Pixnio

Electron micrograph of a mite

Electron micrograph of a typical dust mite • CSIRO (CC BY 3.0)

A very small world

Ever since I start­ed work­ing on this col­umn my eye­lids have been itch­ing, and I’ve been invol­un­tar­i­ly scratch­ing at my wrists and the gaps between my fin­gers. It may be psy­cho­log­i­cal­ly induced, but I swear that I feel them — the invad­ing hordes, the micro­scop­ic mon­sters, the aliens.

Image of bacteria

Image by Josef Reischig (CC BY-SA 3.0)

Image of E. coli

Escherichia coli • NIAID (CC BY 2.0)