Our work is a combination of field and laboratory experiments to determine how and why some marine molluscs detect and orient to the geomagnetic field. We have identified a pair of neurons in the brain that respond electrically when the ambient magnetic field changes direction. More recently we also discovered that these neurons make a unique trio of peptides which regulate ciliary activity on the foot of the animal (and elsewhere). Our present work focuses on defining the roles of geomagnetic orientation in the ecology of the animal, on the molecular and receptor level interactions of the ciliomotor peptides on their target tissues, and we are especially interested in the fundamental mechanisms of primary sensory transducers for geomagnetism.