A plant culturing technique in which immature pollen is made to divide and grow into tissue (either callus or embryonic tissue) in either a liquid medium or on solid media. Pollen-containing anthers are removed from a flower and put in a culture medium; some microspheres survive and develop into tissue. If embryonic tissue develops, it's put in a medium favorable for shoot and root development; if it's callus tissue, it's put in a solution of hormones that will spur it to differentiate and develop shoot and root tissue.