Helion's unorthodox approach to fusion power and relative secrecy has earned it plenty of fans — and critics. But don’t count its investors among the naysayers.

Microsoft-backed startup now valued at $5.4B Fusion energy startup Helion has yet to prove it can generate electricity, but that hasn't stopped investors from dumping another $425 million into the venture.

A nuclear fusion startup backed by OpenAI founder Sam Altman has raised nearly half a billion dollars to build what it hopes to be the world’s first power plant using the next-generation energy source. US-based Helion Energy recently unveiled its latest prototype in Everett, Washington, before announcing a $425 million funding round this week.