“The work is never complete, because there is no perfection or completeness,” the artist Lee Ufan once told The New York Times. “Maybe it’s because I’m Asian. One day I’ll be happy with it, and the next day I’ll want the museum to change it.” Ufan is 87 years old. He first came to Düsseldorf for an exhibition at the Kunsthalle 50 years ago, before founding the artists’ collective Mono-ha, Japan’s first internationally acknowledged contemporary art movement. The principle was simple. When he realized an artist’s ability was nullified by technology, he decided on “not making.” He put simple steel and stone sculptures in a room and examined their interactions with the viewer. After the mid 60s, the group quietly disbanded, but Ufan would continue his minimalist studies. This show includes work from the last five decades of his career. Don’t miss his artistic intervention in the Rembrandt Room at the Gemäldegalerie. —Elena Clavarino