Plutonium is one of the most lethal substances known to us. Unfortunately, huge quantities of this radioactive element are produced in certain types of nuclear reactors and has to be stored in safe places. Because of its low solubility in water, it was presumed that it would pose no danger to groundwater. But traces of plutonium were discovered in groundwater 30 km from a Nevada nuclear test site in the US. Now, a study at Livermore Laboratory and Los Alamos National Laboratory has shown how colloids like clay and zeolite in the soil could facilitate the process by which plutonium contaminates groundwater. This is significant since any long term or permanent storage strategy needs to consider the possibility of its leakage into the groundwater ( Physics Today , April 1999).