Successful microinjection of sperm or sperm nuclei into oocytes depends upon many factors. For example, injection needles must be large enough to pick up a sperm (nucleus) yet not so large as to kill the oocyte. The suction/pressure system should be very precisely controlled so as to minimize injection of excess fluid into the oocyte. As is true of other micromanipulation procedures, the microscope should provide a wide range of magnifications, long working distance, and a fixed stage; and, chambers must allow for easy addition/removal of oocytes with minimal disturbance of micropipet position. With all of these components operating together, the time required to inject small groups (or single) oocytes can be minimized thus avoiding, as much as possible, excessive oocyte aging and the deleterious effects of adverse environmental conditions outside of the incubator.