Science: The self-assembly of block copolymers into nanoscale features is potentially attractive as a means for patterning media in microelectronic applications. This new route to nanopatterning is gaining interest as optical lithography, the current engine of the semiconductor industry, begins to approach intrinsic technological limits while demand for higher-density features for improved data storage and computing speed continues to grow. These applications require not only regularly sized nanoscale features but also a degree of perfection of order and registry relative to other components, which have so far been elusive in self-assembled systems. In this week's issue of Science, two papers ( Graphoepitaxy of Self-Assembled Block Copolymers on Two-Dimensional Periodic Patterned Templates and Density Multiplication and Improved Lithography by Directed Block Copolymer Assembly) describe how block copolymers in conjunction with coarse templates are used to create nanoscale structures with an unprecedented level of control.