At the top of the uterus, the remaining sperm face a literal fork in the road: two fallopian tubes.

: Once a single sperm fuses with the egg membrane, the egg undergoes conformational changes to become impenetrable to any other sperm, ensuring only one set of male chromosomes enters. Potential Search Mismatches

In that interview, Thompson claimed he was a former microbiologist who turned to acting after “witnessing the arrogance of human reproduction firsthand.” He described his performance in The Sperm Invasion as “method acting to an extreme—I lived for three weeks in a warm, dark room with only nutrient broth for sustenance.”

For the surviving sperm, the next challenge is the cervix. Guarding the entrance to the uterus is cervical mucus.