people across the globe. The Industrial Revolution in the 18th and 19th centuries, which led to the discovery of steel, oil, gas and electricity changed where and how people lived. Large metropolitan cities sprang up as technology allowed the construction of tall, structurally safe stable buildings. Gas engines made the world smaller. Oil lamps, followed by electricity, extended the time when activities that were previously limited to daylight hours could run deep into the night. All of these inventions