Fungi are organisms with life cycles that exhibit both a haploid phase and a diploid phase. During the haploid phase, reproduction is conducted through gametes, or a mature reproductive cell (male or female) that units with the opposite sex and fuse together to form a zygote. During the diploid phase, reproduction is conducted by spores, which develop individually and divide through mitosis, producing the gametophytes (sexual form of a plant) of the next generation. (For more information about mitosis, see the chapter “Cellular Basics.”)