org-emph-re

org-emph-re is a variable defined in `org.el'.
Its value is

"\\([ 	('\"{]\\|^\\)\\(\\([*/_=~+]\\)\\([^ 	
\n,\"']\\|[^ 	
\n,\"'].*?\\(?:\n.*?\\)\\{0,1\\}[^ 	
\n,\"']\\)\\3\\)\\([- 	.,:!?;'\")}\\]\\|$\\)"

Documentation:
Regular expression for matching emphasis.
After a match, the match groups contain these elements:
0 The match of the full regular expression, including the characters
before and after the proper match
1 The character before the proper match, or empty at beginning of line
2 The proper match, including the leading and trailing markers
3 The leading marker like * or /, indicating the type of highlighting
4 The text between the emphasis markers, not including the markers
5 The character after the match, empty at the end of a line