Ink jet ink composition

An ink jet ink composition comprising water, humectant and a nanoparticulate dispersion that is the product of self-assembling colorant molecules that spontaneously form the nanoparticulate dispersion without any prior physical attrition or prior surface modification, said self-assembling colorant molecules each represented by the formula:

• (A)m—Q—(Z)n
• wherein:
• Q represents a chromophore;
• each A independently represents an organic or inorganic non-ionic, hydrophilic group capable of hydrogen bonding or other non-covalent bonding to form the nanoparticulate dispersion;
• each Z independently represents an organic or inorganic water-solubilizing group capable of electrostatic bonding to form the nanoparticulate dispersion;
• and
• m and n each independently represents an integer from 0 to 10;
• with the proviso that n+m is at least 1;
• and with the further proviso that at least about 50 wt. % of the colorant is present in the composition as particles.