One challenge faced by researchers studying global urbanization is that different countries have different definitions of what constitutes an urban settlement. Many countries define urban settlements based on the number of people living in them. However, countries do not all use the same number; for example, Greenland uses a minimum population of 200, while Benin uses 10,000. Other countries use a combination of population and other factors, like how close buildings are to each other. This variation makes it difficult for researchers to compare aspects of urbanization in different countries.

The following text is from Yung Wing's 1909 memoir My Life in China and America.

We landed in New York on the 12th of April, 1847, after a passage of ninety-eight days of unprecedented fair weather. The New York of 1847 was altogether a different city from the New York of 1909. It was a city of only 250,000 or 300,000 inhabitants; now it is a metropolis rivaling London in population, wealth and commerce. The whole of Manhattan Island is turned into a city of skyscrapers, churches and palatial residences.

The following text is adapted from Matthew Arnold's 1869 nonfiction book Culture and Anarchy.

The Times [a British newspaper], replying to some foreign strictures on the dress, looks, and behaviour of the English abroad, urges that the English ideal is that every one should be free to do and to look just as he likes. But culture indefatigably tries, not to make what each raw person may like, the rule by which he fashions himself; but to draw ever nearer to a sense of what is indeed beautiful, graceful, and becoming, and to get the raw person to like that.

Humans aren't the only ones who use tools. Other animals also find tools helpful. Octopuses use two halves of a seashell to provide protection or a place to hide. And despite sometimes being thought of as simple, many birds make clever use of tools as well. New Caledonian crows are well known for creating hooks and spears from twigs. Furthermore, palm cockatoos have been observed using leaves to pad their beaks when opening nuts.

Women like Minnie McNeal Kenny made important early contributions to the history of US cryptology, a field concerned with secure data communication and storage. Kenny worked for the National Security Agency (NSA) and received the NSA's two highest awards. She also held administrative positions at the National Cryptologic School. In this way, Kenny and others like her helped make it possible for more women—such as Anna Lysyanskaya, who currently works in and teaches digital cryptography—to enter the field of cryptology.