The mechanisms underlying the differentiation of neocortical areas are still largely unknown. The development of neural connectivity constitutes one important step in neocortical differentiation. One way to study the mechanisms guiding this developmental stage is to examine the connections established by transplants of neocortical tissue of varying embryonic age placed in varying areas of the neocortex of newborn hosts. Neurotracer injection into the transplant at different intervals following transplantation is then used to identify the development of host-transplant connectivity. In most cases, however, it is rather difficult to retrieve the transplant within the host cortex even shortly after grafting. Hence, it is very difficult to perform tracer injections limited to the transplant without any involvement of the host cortex. In some instances, the transplant position can be predicted by some weaker vascularization within or at the surface of the graft. This is not, however, a reliable criterion to establish the rostrocaudal and mediolateral coordinates of the tracer injection. In this report, we describe the use of activated charcoal to mark the transplant at the time of transplantation. The transplant containing black dots can subsequently be easily distinguished from the host pale pink cortex.