Cover picture: Confocal focal observation profile images in log-scale pseudocolor for a 1.2 NA objective for various sizes of confocal aperture and fraction underfilling of the objective back aperture. The log scaling emphasizes the fringes causing departure from the ideal ellipsoidal Gaussian focal observation profile which can introduce errors of analysis in fluorescence correlation spectroscopy. The ideal Gaussian ellipsoidal observation volume is more readily achieved with two-photon laser microscopy but can be approximated in confocal one photon excitation by selection of a small confocal aperture and underfilling the back aperture. See the article by Hess and Webb on p. 2300.