Small caps have many uses, but are primarily used for initials in body copy, such as NASA, NATO or the UN. The aim of this use is to diminish the visual awkwardness of capital letters hindering the flow of a paragraph. (Text figures are also used for better flow in body text versus lining figures.)
The OpenType feature registered for small capitals is smcp, there is also a feature registered for petite caps (pcap).
From Nick Shinn:
Here are some differing strategies for “Caps with Small Caps” titling.
I don’t think any of them are ideal for this typeface.
In the designated small cap font the small cap is, as I said earlier, too wide.
You get better matched letter proportions by “faking” the display small cap with a downsized “normal” cap, but the stem widths don’t quite match.
My preference for the best match is the Regular with SemiBold, although it might be a bit heavy overall.

To demonstrate that the situation is not a fault of any particular typefaces, but rather the outcome of the general habit of creating small caps primarily in relation to lower case, I’ve created an alternate small cap for Goudy, matched to the capital.

There may be other genres of type where the caps and small caps are better matched, and some typefaces where the small cap is matched to the cap rather than the lower case, but it is my opinion that in general, old style faces are configured like Minion and Goudy, making the use of caps/small caps in titling problematic, and requiring quite discriminating typography.
See Also:
Mid-Capitals,SmallCaps How-To.
Discussion:
Using small caps
- Appropriate use of small caps
- How to Use Small Caps Correctly
- Type Crime? Title in Small Caps
- Small caps or not?
- How to properly typeset a.m. and p.m.
- Using small caps in scientific texts?
- Apostrophe in Small Caps
- Is "standard" procedure to do small caps with diacritics?
- Rules for Small Caps
- Plural words that require small caps: Contains Nick Shinn's argument for multiple types of "Small Caps".
- Medium Capitals
- Small Caps: the older I get the less I know.
- Fonts with mid-caps?
- Lack of small-cap height lining numerals.
- Setting Irish Names in Small Caps
- Drop Caps (and critique?) Discussion of small caps with drop-caps.
- Correct use of small caps at the beginning of a paragraph
- Capitalized words opening a chapter
- god and the rebellious typographer
- Cpsp feature
Designing small caps
- SmallCaps How-To
- Caps to small caps: Making your own small caps.
- Smallcaps Height Standards
- OpenType smallcaps in a separate font?
- Greek Polytonic Small Caps: is it worth doing?
- Small Cap Versions of fi, fl, and German double s
- Small Capital Eszett?
- Small release of several python scripts
- How to program features into font
About small caps
- History of Small Caps
- Is any Unicode standard that define "small capital" characters?
- Unicode Capitalization and Small Capitals
- True cut small caps?
Additional Articles:
- FYTI: Small Caps
- For the history of small capitals, see M.M. Smith, 'The pre-history of "small caps": from all caps to smaller capitals to small caps', Journal of the Printing Historical Society 22 (1983), pp. 79–106.


