  It is proposed to create materials with a desired refraction coefficient in a
bounded domain $D\subset \R^3$ by embedding many small balls with constant
refraction coefficients into a given material. The number of small balls per
unit volume around every point $x\in D$, i.e., their density distribution, is
calculated, as well as the constant refraction coefficients in these balls.
Embedding into $D$ small balls with these refraction coefficients according to
the calculated density distribution creates in $D$ a material with a desired
refraction coefficient.
