In this activity, learners build a simple solar oven out of household materials to melt chocolate and marshmallow between graham crackers--known as s'mores. This box and foil solar oven is a good introduction to solar energy and the greenhouse effect for learners. Includes step-by-step instructions, reflection questions, extension ideas, and a simple explanation of the greenhouse effect. An optional student observations worksheet within the activity guide is useful if leaners have access to a thermometer. A Spanish version of the activity is also available.