What is formed immediately after a sperm fertilizes an ovum?

When a sperm fertilizes an ovum, the first cell that is formed is called a zygote. This single-cell structure contains genetic material from both the sperm and the egg, establishing a new organism's unique genetic identity. The zygote is a vital stage in human development because it represents the beginning of cell division and the eventual formation of an embryo.

Following fertilization, the zygote undergoes multiple rounds of cell division as it travels down the fallopian tube toward the uterus. Once it divides sufficiently, it transforms into a stage called a blastocyst before implanting into the uterine lining. Only later does it develop into an embryo and eventually a fetus as the structures and systems of the body continue to form over time. This makes the zygote the foundational stage immediately following fertilization, setting the stage for subsequent developments in embryonic growth.