An aeolipile is an ancient device that demonstrates the principles of steam power. It consists of a hollow sphere or cylinder mounted on a pivot, with one or more nozzles that expel steam. When heated, the steam escapes through the nozzles, causing the device to spin. This simple mechanism is often considered one of the earliest examples of a steam engine. The aeolipile is attributed to the Greek engineer Hero of Alexandria, who described it in his work around the first century AD. While it was primarily a novelty, it laid the groundwork for later developments in steam technology, influencing the design of more complex engines.