life sciences and material science. In this work we focus mostly on how quantum technologies could be applied to one of them – nonlinear microscopy, and whether it possible to have the best of both worlds – high penetration depth, spatial and temporal resolution of well-developed nonlinear microscopy techniques implemented in a low-light regime of quantum optics setting. Nonlinear processes in optics are known for their inefficiency due to the low probability of 3, 4,..n-particle interactions. However, theory predicts linearization of these processes when the photons which are involved in the interaction are entangled. In virtue of maturity of entangled-pair generation techniques, the linear dependence of entangled photon absorption on the number of entangled pairs has been observed experimentally for several molecular systems. However, studies did not demonstrate a link between pair properties and the absorption rate. In order to establish this link and to find what entangled two-photon absorption depends on and what properties it possesses, we excited a Rhodamine 6G solution by an entangled pair beam and used a photon collection and detection system to see whether any entangled pair-induced fluorescence can be observed and how its rate behaves as a function of entangled beam properties. We ruled out all possible contributions of the signal to unambiguously demonstrate entangled two-photon absorption. We studied an influence of an interphoton temporal delay and polarization on the absorption rate in a liquid Ethanol solution of Rhodamine 6G for different concentrations. We found that the entangled two-photon absorption is sensitive to the interphoton delay on femtosecond time scale without any dependence on the relative polarization within an entangled pair in the case of unpolarized absorber. One of the most popular methods to study properties of a nonlinear process is Zscan technique. To further study the link between pair properties and the absorption rate in the light of nonlinear microscopy, we investigate spatial behavior of entangled two-photon absorption in the same dye we modified this technique and performed a fluorescence-based Z-scan on Rhodamine 6G film and demonstrated that entangled two-photon absorption spatial profile is similar to a single-photon absorption one and agrees well with a model of single-photon absorption with given beam parameters. Combined, the observations constitute a demonstration of fundamental properties of entangled two-photon molecular absorption .