His concern, as he outlined in a chapter of his 2014 book, "Undeniable: Evolution and the Science of Creation," was that scientists didn't have a clear picture of what they could do to the ecosystem.

But starting in February, his tune began to change. Late that month, Nye visited Monsanto, a corporation known for genetically modifying agricultural products. Around that time, Nye told Real Time's Miles Leicher that he had "revised [his] outlook."

Nye stepped in for his friend and radio host Neil deGrasse Tyson on this week's edition of StarTalk Radio to discuss his changed views on GMOs. He explained that what changed his mind was a fateful visit to the lab where scientists do the actual gene modification. There, he watched them scan the entire genetic sequence of the crops they wanted to modify.