There are several examples of functional nanosystems in nature: structural colors of butterflies and beetles and the self-cleaning properties of the lotus flower leaf based on superhydrophobic nanostructures. In the present talk I concentrate on functional nanomachinery found in the skin of certain fishes and frogs used to change the color of the skin as a defense mechanism or for social purposes. This machinery is based on pigment particle containing cells, where the distribution of the particles in the cell is determined by hormones under control of the symphatetic nervous system. The particles, with a diameter around 500-1000 nm are strongly light scattering and when dispersed in the cell most of the light is scattered. The dispersion is controlled through rhe hormones via so called G-protein coupled receptors. Since this type of receptors is common in many biological phenomena also in humans, they act as targets for (new) drugs. Studies of pigment particle containing cells lead therefore to new understanding of the action of drugs and to new biosensing possibilities. These items will be discussed in the talk as well as the “physics” behind the pigment particle distribution in the cells. It turns out that it is a complete nanomachinery consisting of chemically driven nano vehicles moving on nano “railroads” inside the cell controlled by nano biosensors, the G-protein coupled receptors.