This is a pile of manioc. This root has many names like cassava or yuca. Brazilians call it mandioca. These roots are a staple of people's diet here. They are tasty potato-like vegetable. You can prepare the manioc by boiling it or frying it. You could even make farinha out of manioc.
Clue #1 No, this photo wasn't taken under a microscope.
Clue #2 It is tasty!
Clue #3 They came from underground.