Houghton Mifflin Harcourt is also a textbook publishing giant, and editors in that division happened to see page proofs of “Thing Explainer,” which attempts to explain concepts like tectonic plates, cells and nuclear bombs using just the thousand most common words in English.

“We just all had an a-ha moment,” said Peggy Smith-Herbst, the senior vice president who oversees content development for science and mathematics. “We always knew we wanted to work with him.”

Houghton Mifflin Harcourt announced on Tuesday that it was collaborating with Mr. Munroe to incorporate parts of “Thing Explainer” into the next editions of its high school chemistry, biology and physics textbooks, to be published this summer. “It’s a way of deepening the engagement level for students,” Ms. Smith-Herbst said.

Mr. Munroe, 31, said the project appealed to him. He recalled as a child a foldout diagram showing different animals at the starting line of a race and then sprinting/flying/crawling to show the different speeds of different species. “For some reason, I fixated on that illustration,” he said. “It stuck with me my entire life.”