This is what's inside a turtle shell. | Insider Science

The structure of a turtle's shell. | IFLScience

Check out the fascinating science behind the evolution of the turtle shell, over 260 million years in the making: | TED-Ed

Depending on the nutrient content of the water in which various turtles live, including sea turtles, they’re known to grow algae on their shells! This is particularly common in musk turtles in springs that have high nitrates, due to the excess nutrient content and lack of basking from the species. To see it on sea turtles is less common, but still very interesting! | DanTheTurtleMan