The multithermal gradient (MTG) technique is based on the principle of directional freezing (Fig. 1), which allows control over ice crystal propagation through a predetermined thermal gradient, by regulating the velocity of the sample movement through this temperature gradient. This method also enables incorporation of controlled seeding into the freezing process. When any liquid is cooled below its freezing point, it remains as a liquid, in an unstable super-cooled state, until freezing starts randomly at distributed nucleation sites and spreads throughout the entire volume of the liquid. When using the conventional method of freezing, ice grows with uncontrolled velocity and morphology and may disrupt and kill the cells in the samples. Ideally, ice crystal propagation should be such that it does not disrupt the cells or tissue. The laterally varying gradient used in our technology allows cooling to proceed at differing rates under varied temperature regimes, thereby facilitating full control over nucleation and ice crystal morphology. This technique allows very precise control of the cooling rate (0.01–1000°C/min) within a large volume. The MTG freezing apparatus can control ice crystal propagation by changing the thermal gradient (G) or the liquid-ice interface velocity (V), thereby optimizing the ice crystal morphology during the freezing process (Fig. 2) (Arav 1999). Thus, maximizing the survival rate of cells subjected to freezing and thawing requires careful control of the freezing process, that is, interface velocity. Using cryo-microscopy observation, we found that survival of sperm had a biphasic curve, where at a very slow velocity, ice will grow in a planar form, which will kill all cells. At higher velocities, ice crystals will form secondary branches and survival will increase; also, at 300 μm/s, ice will start to form ‘needle-like’ ice crystals, which will increase post-thaw motility and will permit very high survival depending on the space between ice crystals (Arav 1999; Arav et al. 2002a,b). Finally, at >3000 μm/s, directional solidification will not occur and survival will decrease. We used directional freezing for freezing and vitrification of many gametes, embryos, somatic cells, tissue and organs such as sperm of domestic and wild animals, oocytes and embryos vitrification, stem cells, ovarian tissue and whole ovaries (Saragusty and Arav 2011).