Here are some tips to help you navigate this site:

• Click on a category in the navigational menu at the top of the site to view thumbnails of images in that category.
• Click on a thumbnail to enlarge it.
• Move the cursor over the top navigational menu to begin a slide show..
• Place the cursor over the enlarged image to pause the slide show.
• Move the cursor over the top navigational menu to resume the slide show.
• Click on the right arrow next to the enlarged image to bring up the next image.
• Click on the left arrow next to the enlarged image to bring up the previous image.
• Click on the icon in the top right corner of a category page to toggle thumbnails or slideshow mode.

Other notes about the site: 

• This site is optimized for Google Chrome, Mozilla Firefox and Internet Explorer 9 or higher. 
• Because of the large number of images it is normal for the thumbnails to load slowly, especially for the abstract categories.
• The navigation of the website differs somewhat when using an iOS device such as an iPad.