Researchers have provided a big new clue to help combat amyotrophic lateral sclerosis (ALS), deciphering that the dense protein aggregates that contribute to the nerve decay of ALS are composed of just one protein: superoxide dismutase (SOD1). While the aggregation of mutated SOD1, a protein that normally protects cells from free radical damage, is a tell-tale sign of familial ALS, the exact composition of these aggregates has been unclear.