Several techniques based on soft lithography have emerged to replicate micrometre-sized patterns. Similar to most other lithographic methods, these techniques structure a single layer of photo resist. For many applications, however, it is desirable to control the spatial arrangement of more than one component. With traditional methods, this requires an iterative, multistep procedure, making the replication process more complex and less reliable. Here, a replication process is described where multiple materials are processed simultaneously. Using a bilayer formed by two different polymers, electrohydrodynamic instabilities at both polymer surfaces produce a hierarchic lateral structure that exhibits two independent characteristic dimensions. A lateral modulation of the electric field enables replication with a resolution down to 100 nanometres. This approach might provide a simple strategy for large-area, sub-100-nanometre lithography.