What is the ball of cells formed after fertilisation called?

Fertilization:

The fusion of male gamete(sperm) and female gamete (ova) is known as fertilization.

Post fertilization the cells formed undergoes the following stages :

1. The zygote begins to divide via mitosis after fertilization.
2. The solid ball of cells known as a morula is made up of 8-16 blastomeres.
3. It then divides and differentiates further to form a hollow ball known as a blastocyst.
4. The blastocyst is composed of an outer layer of cells called trophoblast and inner cell mass, which develops into the embryo.