capital letters = link
"complementarity is the Realisation that the behaviour of a particle and a wave, although they exclude each other, are both necessary for a complete description of all phenomena"
complementarity was first used to describe the wave/particle characteristics of substance
this website is using the notion of complementarity to tie together nothing and something and nowhere and somewhere and infinitely big and infinitely small and shape and shapelessness and...
the point is "you can't have one without the other" (sung to the tune of love and marriage)
see also Complimentarity and Superposition