This board book adaptation follows the same format as the original, though slightly shorter in length. Readers are introduced to an egg with one defining characteristic pointed out, such as color, size, texture, or location, and asked the title question. Along with the egg are hints, such as a single ostrich feather, or a sandy beach with a tiny piece of ocean in the corner. The answer is revealed with the turn of the page, and the main characteristic is explained. A robin’s egg is bright blue because the color protects it from strong sunlight. An ostrich egg is the largest egg and can weigh more than three pounds. The realistic gouache illustrations depict the eggs in their natural habitat along with their parents in full detail. Readers might see a colony of emperor penguins with dads protecting their eggs from the snow and ice, or a small dinosaur hatching from a clutch of eggs in a prehistoric setting. Most eggs come from birds, but there are a few reptiles too, like the dinosaur and the loggerhead sea turtle, though the board book doesn’t show the mammal egg layer, the platypus. The final two pages show a few “eggcellent” egg facts, which will probably be less appreciated by a toddler audience than the bright pictures and simple statements of the earlier pages. Still, this is a fun introduction to a common element in the natural world.
—Children's Literature

Children are invited to guess which animal laid each mysterious egg in this charming board book adaptation. Short, factual clues pair with naturalistic illustrations, encouraging close observation and early scientific thinking. Oseid’s artwork scales beautifully, making the science approachable for little hands. This book turns learning into a playful, fact-filled game. VERDICT A smart and inviting pick for those growing the early nonfiction shelves.
—School Library Journal