Transition Ventures' second fund has closed at over $150M, bringing AUM to $300M. David Helgason, founding CEO of Unity Software (NYSE: U), spent two decades giving developers the tools to build virtual worlds. Now, with Transition, he's backing the founders building the physical one. He spoke to Pathfounders Editor Mike Butcher about its pivot towards rarified areas such as photonics and even small modular reactors.