In this Paper Cup Challenge, students of 4th grade (consist of 27 students, divided into 7 groups) explore more and apply their knowledge in science, technology, engineering, and mathematics. The context about this project is the teacher lead the students in to environment issues about plastic cup which can decompose over a long time. It aims to promote environmental awareness and understanding of scientific principles like surface tension while applying knowledge from science, technology, engineering, and math (STEM). By creating paper cups, students explore an alternative solution while engaging in hands-on learning. The students will learn about the principles of surface tension and collecting data based on the amount of water and the duration of the cup that hold water by designing, creating, and testing paper cup. This project encourages creativity, critical thinking, and collaboration while tackling a real-world challenge. A more comprehensive explanation about the project (steps of the lesson and STEM habits of mind) can be seen on the lesson plan and implementation slides.