It begins at puberty.
With a sperm cell and a egg cell.
Life begins when the egg cell and sperm cell unite to form the zygote.
When an egg was fertilized by a sperm cell.
A sperm and an egg.
the egg is larger than the sperm cell
The uniting is known as fertilisation of the egg by the sperm.
FERTILIZATION
Egg cells are the biggest: you could only fit one on the head of a pin. But I'm not sure if a sperm cell is bigger than a red blood cell or vice versa.
Twenty-three chromosomes are in a cell that is formed from a sperm and egg cell.
egg by far
A sperm fused with an egg
The cell that fertilises the egg cell is called the sperm cell. _-------O That's how a sperm cell looks like <<<<<<<<<<<<<<<<<