“All of a sudden you see cells moving.” 
 
 This was not the only instance in which researchers cultivated human tissue on a plant scaffold.
– Popeye knew a thing or two about building muscle, maybe even more than we realized. Per National Geographic, scientists have appropriated the cartoon character's favorite snack—a spinach leaf—to help create new human heart muscle. In doing so, they circumvented a tissue issue that's plagued this type of regenerative medicine and carved a path toward facilitating organ repair down the road. The study published in the Biomaterials journal details that challenge: even though researchers have been able to formulate human heart tissue in a lab, working up the vessels to deliver nutrients to that tissue has been problematic. "The main limiting factor … is the lack of a vascular network," study co-author Joshua Gershlak says in a video on the study. Which is where Popeye's plant food comes in. Scientists at Worcester Polytechnic Institute took a spinach leaf—with its own system of tiny veins to keep it fed and hydrated—removed its plant cells, and then immersed the leaf in a bath of human cells, using the leaf as a "scaffolding" of sorts. They pumped fluids and microparticles through the leaf's veins to demonstrate how oxygen could one day similarly flow through such a vascular system to keep human heart tissue healthy. The researchers were even able to see clusters of the cells "beating" within the leaf. "It was definitely a double take," Gershlak says, per the Washington Post. He and co-author Glenn Gaudette, both bioengineers, came up with the idea while eating lunch one day (which included spinach) and talking about the dearth of donated organs. (In the meantime, please wash that dirty spinach before you chow down.)