A hydrothermal process has been used to synthesize walnut-like maghemite superstructures which can be further self-assembled in a controllable manner into ordered three-dimensional (3D) architectures and one-dimensional (1D) nanochains in the presence of different external magnetic field. The assembly behavior of the maghemite nanoparticles isclosely related to the van der Waals interactions and external field-induced magnetic dipole interactions. The magnetic properties of these nanostructures are also investigated. (C) 2015 Elsevier B.V. All rights reserved.