Even at our cleanest, we are covered in germs and we are full of germs. It's ok! That's totally normal. These microorganisms are essential to our health. You probably don't need to mess with them, but if you'd like to try, the terms to know are prebiotics and probiotics.

Sweaty clothes stink, but sweaty workout clothes stink worst of all. Like those synthetic-fibre leggings, those sweat-wicking socks, those "technical" tees? Phew. These fabrics are especially prone to harbouring the smelliest bacteria.

If you need a really last minute gift, try this nerdy card game you can print on card stock and play today. Gut Check, designed by microbiome researcher David Coil, pits your microbes against opponents': you can contract infections, take probiotics and watch antibiotic resistant genes spread through the population.

By this point, it shouldn't surprise you to know that the world is full of bacteria. But the numbers can still be baffling. Take your body: It probably has 37 trillion cells or so, and maybe the same number of bacterial cells.