Conventional wisdom would have it that diffraction effects will not allow photolithography with features smaller than a quarter of the wavelength of whatever light is used. However, a new trick allows you to go a factor of five better.
John Fourkas of the University of Maryland and colleagues used multiphoton emission from one 800 nm laser pulse to initiate cross-linking in a polymer, following it with a carefully phased second pulse to de-excite molecules by stimulated emission. Done correctly, this leaves an excited region much smaller than the wavelength of the light that is being used.
Further reading
Linje Li et al. 2009 Science 324 910.