In 1992 P. Poole and coworkers have proposed the existence of two water polymorphs below its homogenous nucleation temperature. These are separated by a coexistence line ending in a second critical point. From this point a line of maxima of the correlation lengths (Widom line) originates. Experimental tests of this model have been performed in confined water, that can be easily supercooled. No unambiguous evidence for the existence of the Widom line has been so far published. NIMROD can contribute relevant insights into the vivid debate present in the literature. To this aim, we propose to perform a NDIS experiment on water confined in MCM41 substrates, with different confining sizes, along a temperature path from ambient down to 210 K, at ambient pressure. NIMROD is well suited to evidence at the same time critical fluctuations and/or crystallization.