The heart of growth hacking is the relentless focus on growth as the only metric that truly matters.[18] Mark Zuckerberg had this mindset while growing Facebook.[19] While the exact methods vary from company to company and from one industry to the next, the common denominator is always growth. Companies that have successfully "growth hacked" usually have a viral loop naturally built into their onboarding process.[20] New customers typically hear about the product or service through their network and by using the product or service, share it with their connections in turn. This loop of awareness, use, and sharing can result in exponential growth for the company.[21]