What are the most fascinating examples of symbiosis in nature?

The answer

Symbiosis takes many forms in nature. Clownfish live among the stinging tentacles of sea anemones, protected by a mucus coating, while providing the anemone with food scraps and driving away polyp-eating butterflyfish. Cleaner wrasses set up 'cleaning stations' on reefs where larger fish queue up to have parasites removed from their gills and mouths. Oxpeckers ride on large African mammals, eating ticks and raising alarm calls when predators approach. Perhaps most remarkably, the relationship between mitochondria and eukaryotic cells began as an ancient symbiosis roughly 2 billion years ago, meaning symbiosis literally powers all complex life on Earth.