Blastocyst

A preimplantation mammalian embryo with an inner cell mass, an outer trophoblast layer, and a fluid-filled cavity called the blastocoel.

Blastulation: The developmental process that transforms a morula into a blastocyst. This process creates the cavity and distinct cell populations that define the blastocyst.
Cleavage (embryology): Rapid cell divisions of the zygote that produce smaller cells without overall growth of the embryo. These divisions produce the cell population from which the blastocyst forms.
In vitro fertilization: An assisted reproductive technique in which eggs are fertilized with sperm outside the body. IVF embryos may be cultured to the blastocyst stage before transfer.
Preimplantation embryo: An early embryo before attachment to the uterine lining. A blastocyst is one specific stage within this broader developmental interval.
Blastocoel: The fluid-filled cavity inside a blastocyst. Fluid accumulation in this cavity expands the embryo before implantation.
Morula: A compact, solid ball of cells formed during early cleavage of a mammalian embryo. The morula is the immediate developmental stage before cavitation produces a blastocyst.
Blastocyst culture: The laboratory cultivation of embryos until they reach the blastocyst stage. Culture conditions determine which embryos develop far enough for blastocyst-stage assessment.
Gastrula: An embryo undergoing gastrulation, when cell movements establish the primary germ layers. The gastrula forms after implantation and has a different organization from the blastocyst.
Inner cell mass: The cluster of cells inside a blastocyst that gives rise to the embryo proper and some supporting tissues. Its position and developmental potential distinguish it from the surrounding trophoblast.
Compaction (embryology): A process in early mammalian development in which blastomeres adhere closely and become polarized. Compaction helps establish the outer and inner cell populations of the developing embryo.

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