Nanobots are one of the greatest advancements in medical science that the GHS (Galactic Health Service) has ever created. Developed using joint Human/Turian technology in the year 3446 PLF, Nanobots represent the answer to most, if not all, diseases and ailments imaginable. They are even useful for delaying potential infections from creatures like the Flood and the Virus.
The Nanobots work by using laser and transwarp technology to destroy, remove or otherwise delay potential infections or other such ailments. Many diseases, as well as ailments like cancer and even high cholesterol, have been prevented using this technology.
They were designed to resemble snowflakes as this allows them to pass easily through the bloodstream whilst still being able to utilize weaponry and remain in place if necessary.