A hen's egg is a single reproductive cell sealed inside a calcium-carbonate shell — a self-contained package of protein, fat and water built to nourish a chick. Bland and barely scented raw, it transforms utterly with heat: the white sets opaque and firm, the yolk thickens to a rich, savoury cream, and a faint sulfurous note rises. It is one of the most versatile foods in the kitchen, eaten on its own and woven invisibly into countless dishes.