Architects in ancient Rome used concrete to create many durable structures, some of which are still standing. But the method of how to make concrete was forgotten for more than 1,000 years after the Roman Empire collapsed in the fifth century. A British engineer finally rediscovered the formula in 1756, and now concrete is a prime component in many highways, dams, bridges and buildings. A similar story is unfolding for you. A valuable secret you once knew but lost is on the verge of resurfacing. Be alert.