Meiosis is essential for sexual reproduction in eukaryotes and involves a specialized cell division that serves to halve the diploid chromosome number to the haploid level, ultimately producing sperm or egg cells (also called male or female gametes). In comparison to mitosis, which undertakes nuclear division once following a round of DNA replication, meiosis undergoes two rounds of nuclear division (meiosis I and II) following a single DNA replication. Meiosis I is unique and involves interactions between homologous chromosomes (homologues), including pairing, synapsis, and recombination, followed by their segregation. Meiosis II is similar to mitosis and results in the segregation of sister chromatids. Over the last few decades, molecular genetic studies have provided substantial understanding of the molecular mechanisms involved in the regulation of the meiotic process, using the model plant Arabidopsis thaliana, as well as the monocots rice, maize, and barley. This chapter will describe the fundamental processes of meiotic progression, with an emphasis on recent advances regarding the critical gene functions that mediate and regulate these processes.