Traditionally, scientific knowledge is considered too early for preschoolers to learn and handle. However, recent studies have revealed that preschool children have the ability to learn this knowledge, and it is important for their future development, but a typical kindergarten environment does not have staff with relevant experience, nor the methodology to conduct science lessons. To raise children’s interest in scientific content, it is important to appeal to their innate curiosity. Emerging technologies, such as augmented reality (AR) are promising to raise the level of children’s curiosity and, therefore, motivate scientific learning. However, it remains unclear how preschool children would make use of AR technology as a learning medium for exploring and gaining scientific knowledge. In this study, a product design called “P-dia” is being proposed, which employed a co-design method to gain insight into preschoolers’ preferences and learning behavior. The design contains two parts: an AR magnifier and a learning hub. The AR magnifier makes use of AR as a tool to stimulate curiosity and to encourage free exploration, while the learning hub encloses the learning cycle through interactive learning courses and testing sessions. The preliminary results demonstrate that the design may improve the scientific learning of preschoolers, and the product itself is promising to act as a test platform for research related to AR and children’s learning.