Abstract: Recent progress in Kato related problems revealed that for any elliptic operator in divergence form and with complex coefficients there are two intervals (one is strictly inside the other) which are responsible for all singular operators boundedness related to this elliptic operator. Singular operators can be of Riesz transform type or of square function type, at any rate they all obey this rule. But there is one exception. We show in this joint work with O. Dragicevic that bilinear imbedding related to square functions holds in an interval strictly larger than those, mentioned above. We use a certain Bellman function to prove this claim.