Stem cells are increasingly implicated in maintaining certain cancers. Studies of an intractable type of brain tumour provide hints as to why such cells may underlie the tumours' resistance to therapy.

Are two penises better than one? Not so, implies a study of doubly endowed earwigs. An ancestral behavioural preference for the right penis might have facilitated the loss of the left in species that arose later.

The discovery that parts of a solid helium crystal could flow through other parts without friction ignited physicists' interest. Independent experiments confirm this unusual superflow, but its origin remains mysterious.