Lee Mingwei's multi-part exhibit, "Impermanence" (at the Chicago Cultural Center through 1 July) includes a Guernica made of sand and a room containing multiple configurations of bed and nightstand; but check out the Letter Writing Project: an arrangement of three enclosures that invite you to write that letter you've been putting off. You can have it mailed or leave it for others to read; and reading other people's letters is no small pleasure.