  Let $f: B^n \rightarrow {\mathbb R}$ be a $d+1$ times continuously
differentiable function on the unit ball $B^n$, with $\max_{z\in B^n}
\|f(z)\|=1$. A well-known fact is that if $f$ vanishes on a set $Z\subset B^n$
with a non-empty interior, then for each $k=1,\ldots,d+1$ the norm of the
$k$-th derivative $\|f^{(k)}\|$ is at least $M=M(n,k)>0$. A natural question to
ask is ``what happens for other sets $Z$?''. This question was partially
answered in [16]-[18]. In the present paper we ask for a similar (and closely
related) question: what happens with the high-order derivatives of $f$, if its
gradient vanishes on a given set $\Sigma$? And what conclusions for the
high-order derivatives of $f$ can be obtained from the analysis of the metric
geometry of the ``critical values set'' $f(\Sigma)$? In the present paper we
provide some initial answers to these questions.
