Nuclear energy is having a moment.

Europe recently moved to issue green bonds for the power source, and Germany signaled that it may scrap plans to shut nuclear facilities given the country’s energy crunch. Silicon Valley is also embracing nuclear fusion, an unproven technology that promises abundant, cheap and clean energy in the not-too-distant future.

The new U.S. Senate climate pact includes federal funding and incentives for fusion, building on last year’s surge of financing. Now, companies are getting in on the sector, plowing even more money into ventures that are taking the most difficult paths to make fusion’s promise a reality.