Somewhere in Morelia's historic centre, a teenager strikes a pose and a crowd decides whether it was impressive enough. There is a name for this, and it sounds ridiculous.

What isn’t ridiculous, though, is the effect it’s having on kids across Mexico. Perhaps we were wrong to tell them to get off their phones after all, writes Charlotte Smith.

Somewhere between forty and eighty, the women of Mexico City appear to stop acquiring lines.

Their hair whitens, gravity does its patient work, and still: no crow's feet, none. Bethany Platanella has been keeping count — grandmothers, shop owners, the woman who sells her juice — and at forty-two she is losing badly. These (might) be the skincare secrets that Mexico’s women are hiding.