htaccess subdomain creation

RewriteCond %{HTTP_HOST} ^domain.com$ [NC]
RewriteRule (subdomain)(/.*|$) $1.domain.com/$2 [R=302,L]
RewriteCond %{HTTP_HOST} ^(subdomain).domain.com$ [NC]
RewriteRule (.*) %1/$1 [L]

Source:
http://stackoverflow.com/questions/5445978/htaccess-subdomain