+.TP 8
+.B \-grab
+Normally it colors the boxes with a horizontal or vertical gradient.
+If \fI\-grab\fP is specified, it will instead load a random image,
+and color the boxes according to the colors in that image.
+As the picture fills in, some features of the underlying image
+may become recognisable.
+
+When grabbing images, the image will be grabbed from the portion of
+the screen underlying the window, or from the system's video input,
+or from a random file on disk, as indicated by
+the \fIgrabDesktopImages\fP, \fIgrabVideoFrames\fP,
+and \fIchooseRandomImages\fP options in the \fI~/.xscreensaver\fP
+file; see
+.BR xscreensaver-demo (1)
+for more details.
+.TP 8
+.B \-peek
+This option says to briefly show you the underlying image before
+beginning. The default is not to show the unadulterated image at all.
+(This only has an effect when \fI\-grab\fP is used.)