 During its creators' lengthy run, the series produced many acclaimed storylines and characters that have become central to Marvel, including the hidden race of alien-human genetic experiments, the Inhumans; the Black Panther, an African king who would be mainstream comics' first black superhero; the rival alien races the Kree and the shapeshifting Skrulls; Him, who would become Adam Warlock; the Negative Zone and unstable molecules.The story frequently cited as Lee and Kirby's finest achievement is the three-part "Galactus Trilogy" that began in "Fantastic Four" #48 (March 1966), chronicling the arrival of Galactus, a cosmic giant who wanted to devour the planet, and his herald, the Silver Surfer.