The Food of the Gods (1904)
By H.G. Wells

Every life-form on Earth grows in size sporadically. Mr. Bensington and Professor Redwood discover an ingredient that can make the growth process constant. The animals on their experimental farm became giants. However, the ingredient leaks into the world outside. Gradually, cases of colossal plants, insects, animals, and children are encountered throughout the world. Twenty years later, a league of giants seeks to destroy the tiny world of men.

Available in the Bud Foote Science Fiction Collection, Georgia Tech Library Archives