Zygote Formation:
The zygote is formed when a sperm cell fertilizes an egg cell. This occurs in the fallopian tubes of the female reproductive system.

Cleavage:
The zygote undergoes a process called cleavage, which involves multiple cell divisions without overall growth. The resulting cells are called blastomeres.

Morula Formation:
After several rounds of cleavage, the blastomeres form a solid ball of cells called a morula.

Blastocyst Formation:
The morula undergoes further cell divisions and forms a hollow ball of cells called a blastocyst. The blastocyst consists of two distinct cell types: the outer layer of cells called the trophoblast, which will form the placenta, and the inner cell mass, which will form the embryo.

Implantation:
The blastocyst reaches the uterus and attaches to the uterine lining in a process called implantation. This occurs approximately 6-7 days after fertilization.

Formation of the Amniotic Sac and Placenta:
After implantation, the trophoblast cells continue to divide and form finger-like projections called chorionic villi, which extend into the uterine lining. The chorionic villi and the uterine lining form the placenta, which provides nutrients and oxygen to the developing embryo. The inner cell mass forms the amniotic sac, which surrounds and protects the embryo.

Development of the Embryo:
As the embryo develops, it undergoes various stages of growth and differentiation. The cells of the inner cell mass form the three primary germ layers which will give rise to all the organs and tissues of the body. The embryo also develops a primitive circulatory system, nervous system, and digestive system.

Conclusion:
The sequence of events from zygote till the implantation of human blastocyst in the uterus involves several stages of cell division and differentiation, culminating in the formation of the placenta and the development of the embryo. These processes are essential for the growth and survival of the developing fetus.