You don't need a lot of mouse to make a clone. Researchers at the Riken BioResource Center have managed to clone a mouse using just one drop of normal, circulating blood, the BBC reports. The clone was healthy, lived a normal lifespan, and was able to reproduce. While mice have previously been cloned from things like bone marrow and liver, this method—which is similar to the one that produced the famous cloned sheep Dolly—doesn't involve killing the donor mouse, among other advantages.
"This technique would be applicable for generating genetic copies of invaluable strains of mice, which cannot be preserved by other assisted reproductive techniques," researchers said. They're not the only ones making bold strides in mouse copying either; a linked institute recently managed to create 600 identical copies of one mouse.