Zenefits today said it has raised $500 million in a round led by Fidelity and TPG at a whopping $4.5 billion valuation. The company, which allows small- and medium-sized businesses to manage human resources services in a much simpler fashion, is one of the fastest-growing SaaS businesses ever, and in an interview, Zenefits CEO Parker Conrad said the big round was raised to keep the company growing as quickly as it already is.

http://techcrunch.com/2015/05/06/zenefits-rising-hrs-hottest-startup-just-raised-500-million-at-a-4-5-billion-valuation/