What did Ethel Brown Harvey's experiment on sea urchin's show about the cells of a beginning sea urchin embryo?

Ethel Brown Harvey's experiment on sea urchins demonstrated that the cells of a developing sea urchin embryo exhibit a phenomenon known as "cell determination." She found that even when the cells were separated, they were capable of developing into specific structures, indicating that the fate of the cells is determined early in embryonic development. This work provided crucial insights into the processes of cell differentiation and the inherent potential of embryonic cells to develop into various tissues.