So on Friday there was the shirt with denim shorts, as worn by Alessandra Ambrosio. Today there is the shirt with jeans, as worn classicly, by January Jones, above.
Neatly tuck a patterned shirt into your jeans and hey presto! Suddenly you're all rather polished. It's taking over from the t-shirt and jeans to run your errands in. Shirts are a little more stylish and say "instant outfit" to those around you.
Just check out Victoria Beckham if you don't believe me.

Not that she's ever going to look anything BUT polished, VB steps out in a pair of flared jeans and bright, floral shirt. Lovely. And a new, easy look to copy if you're after one.