They may never pose a challenge to Olympic superstar Michael Phelps, but the "microswimmers" developed by researchers in Spain and the United Kingdom could break a long-standing barrier to improving delivery of medications for cancer and other diseases. They describe the development of tiny, magnetically controlled particles, called "microswimmers," that doctors could use to precisely deliver medicine to diseased tissue. Their report appears in the December 25, 2008 issue of The Journal of Physical Chemistry B.