A reciprocal transplant involves introducing organisms from each of two or more environments into the other(s). Transplant experiments are often performed to test if there is a genetic component to differences in populations. In recent decades the advances of molecular biology have provided researchers with the ability study genetic variation more directly. However, transplant experiments still have the advantages of being simple and requiring little technology. On the other hand, they may require considerable time and labour, and the number of test organisms is often relatively limited.