  Based on the color-spin interaction in diquarks, we argue why some multiquark
configurations could be stable against strong decay when heavy quarks are
included. After showing the stability of previously discussed states we
identify new possible stable states. These are the $T^0_{cb}(ud
\bar{c}\bar{b})$ tetraquark, the $\Theta_{bs}(udus \bar{b})$ pentaquark and the
$H_c(udusuc)$ dibaryon, and so forth.
