The best computer tools are those that just work. (A seemingly unprofound statement, I know, though I’m sure everybody has at least one story of a frustrating, nonintuitive computer program.) ImageJ is just that—a simple, clean-cut, useful tool to annotate and analyze images. It’s not much to look at—a simple toolbar that appears on your screen—but there is much more than meets the eye. This Java program runs on Windows, Mac OS X, and Linux, so you never have to worry about compatibility headaches. It’s fast, compatible with many image types, and offers many analysis functions such as distributions, histograms, and measurements. In addition to the freely downloadable software itself, the ImageJ homepage includes a nice collection of links ranging from imaging toolkits, to image-analysis software, to Java programming.