There are regular toys, and then there are toys that are meant to spark a love of math and science. The latter may be educational and fun, but parents say they often create an extra mess.

STEM (which stands for science, technology, engineering, and math) toys often come in sets that have hundreds of small pieces. One parent told the Wall Street Journal (WSJ) that to solve the issue they’ve come up with what they call a “toy library”– from which their kids can only “check out” a limited number of items per week.

Some of the brands that make these toys have started selling items to help keep their toys organized as well. Douglas Clements, a professor of early mathematics told the Wall Street Journal that having too many toys can cause burnout among kids, saying, “You don’t need them all. It’s more important for kids to go back to the [construction set] and think, ‘What do I do now?'”