Why do nearly 1 million people taking cholesterol-lowering statins often experience muscle cramps? Why is it that in the rare case when a diabetic takes medication for intestinal worms, his glucose levels improve? Is there any scientific basis for the purported health effects of green tea? Researchers have developed a chemical toolkit for manipulating mitochondria in its normal cellular environment. After introducing nearly 2,500 compounds to this platform — many of which are FDA-approved — the researchers immediately discerned new insights into basic mitochondrial function, which in turn revealed why some commonly used drugs have particular adverse effects.