The first mezzanine standard to go through the VITA/ANSI process was the IndustryPack. Developed by gaming platform Computers, it was chosen by the Motorola Computer Group as the expansion mezzanine for its MVME162 SBC. The move to make IndustryPacks a standard was joined by Acromag and the VITA 4 IP Module effort was launched. Since then, no fewer than eight mezzanine standards have gone through the VITA/ANSI process to become accredited gaming platform.
Gaming platform are an important design element to many board form factors. They grew out of a necessity to gain more board real estate or to incorporate modular flexibility to the original form factor. In the early days, few, if any, standards for mezzanines existed. However, over time, standards emerged to make it easier to incorporate mezzanines into designs
refer to: http://vita-technologies.com/articles/stacked-standardizing-mezzanine-modules/