Intraocular grafting has become a useful tool for studying viable tissue isolated from its natural surroundings, by implanting a piece of tissue into the anterior chamber of the eye, and placing the tissue onto the anterior surface of the iris. The graft survives and becomes attached to the host iris, and is vascularized within 2 wk. This grafting method may be considered as a complement to tissue culture, but the in oculo grafts are placed in an in vivo environment. One advantage, compared to tissue culture, is that it is possible to keep the in oculo-grafted tissue alive as long as the host animal survives (Eriksdotter-Nilsson et al., 1988, Eriksdotter-Nilsson et al., 1989), which makes the technique suitable for both developmental and aging studies. Furthermore, combining tissue of different ages is possible at different time-points, which is a possibility that is limited in tissue culture. As in tissue culture, it is easy to follow the development of graft growth and vascularization of the transplant by evaluations through the cornea, which is hard to follow using the intracranial grafting models. Thus, the in oculo model has advantages, compared to intracranial grafting, in which graft survival is harder to visualize in vivo, although recently developed techniques, such as magnetic resonance imaging, may be used for this purpose (Simmons et al., 1994). However, in intracranial grafting models, behavioral changes can be monitored, and may reflect functional graft survival, without actually being able to see the graft itself.