Apartment complexes (known as `insula), public toilets, locks and keys, newspapers, even socks all were developed by the Romans as were shoes, a postal system (modeled after the Persians), cosmetics, the magnifying glass, and the concept of satire in literature. During the time of the empire, significant developments were also advanced in the fields of medicine, law, religion, government, and warfare. The Romans were adept at borrowing from, and improving upon, those inventions or concepts they found among the indigenous populace of the regions they conquered