Art and design museum in the Parco Sempione. Some permanent and some rotating exhibitions. Definitely visit the Casa Lana installation and the Italian Design permanent exhibit.
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.
Giacomo ristorante, bistrot... They are all located on the same street, Via Pasquale Sottocorno, but the rosticceria is the more, let's say, "easy-going" (and the cheapest) of the three.
It's a good place for lunch and dinner - ask for a table at the "giardino interno".
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.