The idea of medical nanotechnology often conjures up the potentially troubling image of tiny machines and devices that both exist and operate far outside the scope of unmagnified human vision. Yet much of what constitutes nanotechnology is purely biological in form and function. For example, strands of DNA and the proteins that make up its structure are mere nanometers thick. Many of the basic functions of life occur on the nanoscale level. Efforts to understand or affect these functions are among the primary fields of nanotechnology. Gene study and gene therapy, two byproducts of medical nanotechnology, have already proven useful for identifying and treating a number of different diseases, sometimes even before symptoms of those diseases present themselves. Even so, genetic nanotechnology and treatments can give as much cause for concern as the idea of microscopic machines at work in the body. The possibility of altering an organism's genetic structure has been a subject of much debate as to what extent such an alteration would be both safe and ethical.