Some scents are at risk of vanishing forever. Artificial intelligence can whip up the formula to recreate a perfume based on its chemical composition. One day, it could use a lone sample to reproduce rare smells at risk of being lost, such as incense from a culturally specific ritual or the smell of a forest that is changing because of rising temperatures. Idelfonso Nogueira at the Norwegian University of Science and Technology and his colleagues profiled two existing fragrances, categorising them by scent family – subjective words such as "spicy" or "musk" commonly used to describe perfume – and so-called "odour value", a measure of how intense a certain smell is. For instance, one of the fragrances scored the highest odour value for "coumarinic", a family of scents similar to vanilla.