  Simple field-theoretical approach to critical phenomena is described. In
contrast to the Wilson's theory, a description in real 3-dimensions space is
used. At the same time the described approach is not the same as Parisi's. Used
subtraction scheme is different from the one used by Parisi, but the main point
is that we treat changes of $T-T_C$ as explicit perturbations. By such an
approach not only the critical domain but also the crossover from critical
domain to domain of Landau theory can be described very simply. Consideration
is restricted to scalar $\phi^4$ model in one-loop approximation.
