You should create attributed string
NSRange range = [formattedString rangeOfString:@"."];
range.length = formattedString.length - range.location;
NSDictionary *normalAttributes = @{ NSFontAttributeName : [UIFont systemFontOfSize:15],
NSForegroundColorAttributeName : [UIColor blackColor] };
NSDictionary *smallAttributes = @{ NSFontAttributeName : [UIFont systemFontOfSize:8],
NSForegroundColorAttributeName : [UIColor grayColor] };
NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc] initWithString:formattedString attributes:normalAttributes];
[attributedString setAttributes:smallAttributes range:range];
and then assign it to attributedText
property of UILabel for example.
UILabel *your_label; // do not forget to create and initialize it
your_label.attributedText = attributedString;
Some other controls like UITextView also can show attributed strings.
May be this CGRect for selected UITextRange adjustment for multiline text? answer could be also interesting for you.