Grand Challenges Explorations seeks transformative and innovative ideas to support the design and development of a new menstrual health and hygiene product that meets key criteria of being responsive to user needs, focusing on discreetness, affordability, and sustainability. Truly disruptive technologies harnessing materials science will be prioritized. Solutions must be designed in response to the needs and preferences of women and girls living in low- and middle-income countries and designed particularly with the future in mind.