Arata Isozaki a metabolist architect deigned Clusters in the Air in 1960-62 for Tokyo. He uses the same joint core system as he did for the City in the Air. The concept of the clusters was to develop a new way to structure housing around Tokyo. The Cluster are suppose to represent leaves from trees which are the housing units and the core represents the trunk of the tree.
preface by Richard Koshalek; essay by David B. Stewart and Hajime Yatsuka, Arata Isozaki: Architecture 1960-1990, [Rizzoli International Publication, Inc., 1191