A group of cells grown in nutrient solution from a single cell is called a cell culture or tissue culture.

Here's a breakdown:

* Cell culture: This term is more general and refers to the process of growing cells outside of their natural environment.

* Tissue culture: This term is more specific and usually refers to the cultivation of a group of cells that have differentiated and organized into a tissue.

Both terms are often used interchangeably, but technically, a "tissue culture" is a type of cell culture where the cells are grown in a way that mimics the organization and function of a tissue.