The scalpel is a wondrously simple and effective tool that has saved many lives. But from the vantage point of a human cell, a scalpel is about as precise as an incoming asteroid. The processes that constitute life and death, health and disease, occur within cells on the scale of billionths of a meter (nanometers). This is roughly the dimension of the DNA double helix, the proteins issuing from the genetic code, and all the other macromolecules that float in the aqueous environment of the living cell. The ultimate medical toolkit is not the scalpel and suturing needle; it is a set of tools small enough to go right inside the cell and repair individual DNA molecules or proteins the way a mechanic adjusts the timing belt on a Honda Civic.

Select from the choices above to read the entire article.