Polonium was discovered in 1898 by Marie and Pierre Curie, the first of the two elements they found while investigating the intense radioactivity of pitchblende. It was Marie Curie's first discovery, and she named it polonium after Poland, her native country, which at the time did not exist as an independent state, having been partitioned among its neighbours. Polonium is a rare, intensely radioactive metalloid, a potent source of heat and alpha radiation. A milligram of polonium gives off enough heat from its decay to glow, and the isotope polonium-210 has served as a lightweight heat and power source in spacecraft and as an initiator in early nuclear weapons, though its extreme toxicity now sharply limits its handling.
Extracting polonium from pitchblende was a herculean task even by the Curies' standards: a tonne of the ore yields only about a tenth of a milligram of the element, a scarcity that meant visible, weighable quantities of polonium were not obtained for years after its existence was first inferred from its radioactivity. Trace polonium-210, absorbed by tobacco plants from phosphate fertilisers and soil, is also present in cigarette smoke, and some researchers have argued it makes a small but measurable contribution to the elevated lung-cancer risk of long-term smokers, a claim debated within toxicology but consistent with polonium's well-documented internal radiotoxicity.