English: 7x speed timelapse video of fish melanophores responding to 200μM adrenaline.

Melanophores are cells found on the skin and/or scales of many aquatic vertebrates including fish and amphibians. They are large cells which contain many dark pigment particles called melanosomes, made dark by the presence of the pigment melanin. These melanosomes are moved along microtubule tracks within the cell by motor proteins and can be rearranged to be dispersed within the cell (maximising light absorption by the melanosomes) or condensed near the centrosome (minimising light absorption). Organisms with melanophores trigger this movement of the melanosomes to change colour in response to stimuli.

In melanophores taken from the organism, in this case on a scale taken from a tilapia fish, this response can be triggered artificially in many ways. In this case 200μM adrenaline triggers the transition from dispersed to condensed melanophore organisation.