Cozy ambient inside, but also with tables on the street, Champagne Socialist is a good place to try natural wines from Europe. You can also go there just to buy a bootle (or more, of course) and drink it at home.

Small home/gallery space featuring various works from the Memphis movement.

Classic Milanese restaurant for a special occasion. Definitely try the risotto!

Flowers lovers! Orto Botanico di Brera is an hidden treasure right in the center of Brera and near by Pinacoteca. The garden is a university and museum, there they organize events and activities for the public and schools. It has an amazing collection of flowers and medicinal plants, plus little corners where you can stop by and enjoy the silence for a bit.

I consider e/c natural wine shop a hidden treasure in Milan. Inside a building with an "Emergency" (that is actually an ONG) plaque outside, the first thing one might think is that is a hospital. Once passing the wall, there's a cute internal square, with Basilica di Sant'Eustorgio view. You can sit both inside or outside, which a strongly recommend for spring and summer days. A nice place for just passing by to grab a bottle of wine and drink it at home, having a glass of wine (they have many options) or enjoying a relaxed evening.