Alexander von Humboldt was the most admired scientist of his day. But the achievements for which he was most celebrated in his lifetime always fell short of perfection. When he climbed the Chimborazo, then believed to be the highest mountain in the world, he did not quite reach the top; he established the existence of the Casiquiare canal, between the great water systems of the Orinoco and the Amazon, but this had been well known to local people; and his magisterial work, Cosmos, was left unfinished. This was no coincidence. Humboldt's pursuit of an all-encompassing, immersive approach to science was a way of finding limits: of nature and of the scientist's own self. A Longing for Wide and Unknown Things portrays a scientific life lived in the era of German Romanticism -- a time of radical change, where the focus on the individual placed a new value on feeling, and the pursuit of personal desires. As Humboldt himself admitted, he 'would have sailed to the remotest South Seas, even if it hadn't fulfilled any scientific purpose whatever'.