With the integration of engineering into science instruction, teachers have been seeking ways to add engineering in their classrooms. This article presents a primary (K-2) STEM unit that took place in a half-day kindergarten classroom as a way to address the scientific and engineering practices (dimension 1, p.41) and the disciplinary core idea ETS1: Engineering design found in "A Framework for K-12 Science Education" (NRC 2012, p. 204). More specifically, this unit addresses the science and engineering practices #1, asking questions defining problems (p. 54) and #6, designing solutions (p. 67). This unit, Designing Animal Habitats, is the product of the PictureSTEM project, an ongoing initiative to design curriculum that uses picture books to help facilitate meaningful STEM learning in elementary classrooms, with an emphasis on engineering design. PictureSTEM units use national standards to determine mathematics and science content students are already learning and build an engineering design challenge based on this learning. This allows students to have firsthand experience both with engineering and with using their science, technology, and mathematics knowledge to solve problems. The unit consists of five pairs of literacy and STEM-content lessons (see Table 1), and for this article the authors focus on the science and engineering activities.