You’ve probably overlooked the solution countless times. It’s built right into WordPress. No plugin needed.
The simplest way is probably to do it when you upload your photo in your media uploader. In the image editing screen that pops up when the image is uploaded, you will notice a text box for your caption about midway down the page. Just pop your caption in there, and you’re all set.
And here’s the result.
Although this can vary with your theme, you’ll typcially notice that WordPress automatically puts you image in a nice frame with space at the bottom for the caption. And if you put a long caption in the box, the system will automatically expand to contain it.
You can also access captions for your images via the Media Library.
If you’d like to play around with the style of your captions, then search your theme’s stylesheet for .wp-caption. (Appearance > Editor > Stylesheet – style.css) You’re likely to come across a number of different instances.
Photo: Beautiful Sceneries in Photos on Green Field Background from BigStock