Canada.com reports on the more promising and widespread approaches to the use of nanoscale engineering in cancer therapies: "The [study] involved engineering nanoparticles embedded with the cancer drug Taxotere. The particles were then injected directly into human tumours created from prostate cancer cell lines and implanted into the flanks of mice. ... The technology being tested involves a nanoparticle made of a hydrogen and carbon polymer with bits of drug bound up in its fabric and attached to a chemical that hones in on cancer cells. The polymer gradually dissolves, exposing the nuggets of drug little by little." Killing cells is easy, but killing specific cells is very hard. Accurate, targeted delivery is the hard problem of the day.