In the cold days of the winter we prefer wearing clothes that warm us up and keep us cozy. Among all the possibilities you can find, there's one that stands out and has become the trendiest winter must-have. Everyone is wearing it, from celebs to your colleague (that one that is always impeccable). I'm talking about leather leggings! You can wear them from day to night, and if you style yourself properly you can even go to the office with them. You don't believe it? Well, have a look!