Many young children come to school with prior experiences planting seeds in a garden or in a pot, watering them, and seeing them grow. These early scientific investigations are designed to help children understand that seeds need water, something to grow in (such as soil), and the right temperature to sprout--if these conditions are met, a seed will grow into a plant. The "Seeds in a Bag" formative assessment probe is designed to uncover students' use of a crosscutting concept--cause and effect--related to germination of a seed (Keeley 2013). The study by Russell and Watt shows that young students understand that seeds need water, but do they know what the cause-and-effect relationship is between the water and the seed? This probe is designed to uncover whether they merely know that planted seeds need water in order to grow into a plant, or do they recognize that the seed must take in the water that is added to the soil in order to grow? Overall this probe shows the importance of combining the cause-and-effect crosscutting concept with the disciplinary core idea in an investigative context.