Due to not having laws that slowed down or stopped scientific research, many intelligent scientists from above the ocean moved to Rapture and made many new discoveries. This allowed Rapture to develop very quickly. The most important discovery is the discovery of ADAM. ADAM is a liquid that comes from sea slugs that can rewrite a person's genetic code. This allows people to have special powers like shooting lighting bolts, shooting fire, and lifting objects without touching them. However, ADAM was also extremely addictive, and if users of ADAM went through long periods of time without it, they would suffer serious health problems and go insane. People who got withdrawals from ADAM would turn into Splicers. Unfortunately, many people in Rapture also became addicted to ADAM, and ADAM became something everyone in Rapture wanted and needed. Since ADAM had such a high demand and low supply, young girls called Little Sisters were raised to collect ADAM from dead Splicers. As Splicers would try to kill Little Sisters to take the ADAM they collected, Big Daddies were created to protect the Little Sisters. Big Daddies would kill anyone who attacked a Little Sister.