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Each of us was the grand prize in an ultimate reality competition, the amazing race a sperm makes on the road to fertilization. Millions of sperm compete while overcoming armies of antibodies, treacherous terrain and impossible odds to reach their single-minded goal. To illustrate the full weight of the challenge, Sizing Up Sperm uses real people to represent 250 million sperm on their marathon quest to be first to reach a single egg.

Watch the full National Geographic: Sizing Up Sperm movie online at no cost in high-definition (HD) quality. No downloads needed—simply click to play and experience the excitement with English subtitles included for your convenience.