Complex sentence: Meiosis begins with one diploid cell containing two copies of each chromosome--one from the organism's mother and one from its father--and produces four haploid cells containing one copy of each chromosome.
Split into simpler sentences: Meiosis begins with one diploid cell containing two copies of each chromosome--one from the organism's mother and one from its father. The cell divides twice, potentially producing up to four haploid cells containing one copy of each chromosome.