First, the plaintiff must have suffered an "injury in fact"—an invasion of a legally protected interest which is (a) concrete and particularized, see id., at 756; Warth v. Seldin, 422 U. S. 490, 508 (1975); Sierra Club v. Morton, 405 U. S. 727, 740-741, n. 16 (1972);[1] and (b) "actual or imminent, not `conjectural' or `hypothetical,' " Whitmore, supra, at 155 (quoting Los Angeles v. Lyons, 461 U. S. 95, 102 (1983)).