Design activities can serve as a concrete experience to address the similarities and differences between science and engineering, and also demarcate engineering from tinkering. They can lay the foundation for concept development of targeted disciplinary ideas. Minor, but crucial, changes to classroom tinkering activities along with targeting and carefully scaffolding to science and engineering concepts are essential for promoting discipline-specific and integrated STEM learning outcomes, while also accurately portraying disciplinary expertise that interdisciplinary efforts draw upon.