Steroids tickle cells inside and out.

Discusses research which described a transcription-independent signaling pathway of the steroid progesterone. How steroid hormones cross into cell membranes; Previous research in intracellular steroid receptors; Research by Grazzini et al in this issue; Progesterone activity outside cells; Pharmacology and intracellular receptors; How 5-beta-dihydroprogesterone works; Steroid activity inside cells; Diversity of steroid actions.