In 1996, pharmaceutical giant Pfizer set out to cure angina pectoris (a symptom of heart disease). In their quest, they developed a pill known as UK92480. Unfortunately, this little blue pill didn’t actually produce the expected results... but it did contain what proved to be a very lucrative side effect, and it became one of the best-selling drugs in the world – Viagra. It’s estimated that seven Viagra pills are sold worldwide every second – that’s 604,800 per day!