Soap is sodium salt of fatty acids (RCOONa) which when dissolved in water dissociates to give RCOO- and Na+. The RCOO consists of polar group COO which is hydrophilic and stays at the surface and the non polar group R which being hydrophobic stays away from the surface. At high concentrations RCOO ions are pulled into the solution to form spherical aggregates with R pointing to the centre COO- part remaining outward. This aggregate is known as ionic micelle.