Sexual reproduction is the process in which gametes from two different sex combine together to form a new individual.
The first stage of sexual reproduction is meiosis or gametogenesis. In this stage the diploid number (2n) of chromosomes reduced to a haploid number (n).
In the next stage, the two gametes, both having haploid number (n) undergo fertilization and forms diploid zygote (2n) and the original number of chromosomes is restored.
Then the diploid zygote undergoes mitosis and cell differentiation to form an embryo or offspring (2n).