This hands-on activity gives students the opportunity to use skills and concepts developed in a unit on cells with an unknown organism. They are asked to design and complete a controlled experiment which attempts to answer a simple question about the slime mold Physarum. The activity includes background information, preparation time, abstract, materials, procedure, evaluation, and additional thoughts. The activity is part of The Access Excellence Fellows Collection, an archive of the favorite classroom activities submitted by high school biology and life sciences teachers participating in the Access Excellence program.