By adjusting the concentration of the solution of hyperbranched poly(o-hydroxyamide)s and spin-coating the solution on a silicon wafer, the ultrathin films could be obtained. After heating, the obtained ultrathin films could be converted to the corresponding polybenzoxazole ultrathin films, which have high thermal stability, good durability, and toughness. They are expected to find applications in various fields in the near future. The cover design was created by the first author, Mr. Hiroyuki Maekawa. DOI: 10.1002/pol.20230659
