A new technique for precisely targeting molecules within cells is paving the way for safer medicines that are free of side effects. Researcher J. Julius Zhu and his colleagues have developed a way to manipulate molecules from compartment to compartment within individual cells. The same molecules do different things depending on their location the researchers determined. By manipulating the molecules scientists can determine exactly which locations to target while avoiding locations that would cause harmful side effects. The problem with side effects is caused because you just could not distinguish the molecules doing different things in the same cell said Zhu.