About the cover

February 2011 Volume 7 No 2

High-order harmonic generation is a nonlinear optical process that enables the creation of light pulses at frequencies much higher than that from a seed laser. The host medium for this interaction is typically a gas. Now, the process has been observed in a bulk crystalline solid, with important implications for attosecond science. Letter p138; News & Views p97

Cover design by Greg Stewart