Abstract <p>The influence of low-intensity non-thermal electromagnetic waves of the millimeter range on the surface and volume properties of water, saline, and DNA solutions was studied. It is demonstrated that non-thermal millimeter electromagnetic waves (MMEMW), which coincide in frequency with the resonant frequencies of water structures’ oscillations, produce a specific effect in vivo and in&#xa0;vitro [1–3], affecting living organisms through the aqueous component of their environment. The non-thermal EW is not absorbed by the surface layer of aqueous solutions and penetrates the deeper layers of liquid, leading to the dehydration of salt ions and DNA, and an increase in the density of the aqueous solutions. Irradiation of DNA solutions with low-intensity resonance frequencies for aqueous molecular structures for 90 minutes leads to an increase in the thermal stability of DNA by approximately 1°C. As the temperature increases, the density of non-irradiated and irradiated solutions decreases. However, there is a significant difference between the behavior of density dependence on temperature for non-irradiated and irradiated saline and DNA solutions. Calculations show that for studied solutions, the coefficient of thermal expansion (α) increases with increasing temperature, and the growth of α occurs differently for water structures irradiated and not irradiated with resonant oscillation frequencies.</p>