The inward migration of cells from the blastula during gastrulation.
The process by which a potentiality enters into actuality.
The act or process of entering or intruding.
The spread of cancer cells, bacteries and such to the organism.
A military action consisting of armed forces of one geopolitical entity entering territory controlled by another such entity, generally with the objective of conquering territory or altering the established government.
The breaching of the skin barrier.
The entry without consent of an individual or group into an area where they are not wanted.