  We report an experimental investigation of spreading then shrinking of a
surfactant droplet at the air-water interface with fingering instability
appearing at the edge of the droplet stain. We find out that a droplet of a
surfactant on the water shows three regimes of spreading, shrinking and resting
at the appropriate parameters values. These regimes can be distinguished by
measuring the mean square displacement of the droplet parts, fractal dimension
of stain, or radius of fingerless part of the stain (to measure it, we define
the angular box-counting dimension), versus time. The shrinking regime is a
novel phenomenon.
