Buy-and-sell apps have become super popular in Spain. That reminds me of when my grandma would mend socks.

- What are you doing with that wooden egg, Grandma?

- Just darning your socks.

- Really? That takes patience. Don't sweat it too much, Grandma. I like them well-ventilated. Think of your eyes! At this rate, you're going to need glasses as thick as a soda bottle's bottom.

Grandmas are so cool. Never understimate one. They seem like they don't notice anything but they are actually walking databases. Anyway, no more digressions. Let's get back to second-hand apps.

People usually use them to get rid of stuff they don’t need anymore. You can sell almost anything : your old bike, your car, your comics, your cat...

I think it’s a brilliant idea. Without these peer-to-peer marketplace apps, most of those items would probably end up in landfills. They’re like 24/7 yard sales. Want to get a potty with pedals? Just browse. People get rid of the most unbelievable things.