The scientist who proposed that the nucleus was the structure responsible for the development of the rest of the cell was Robert Brown.

While Brown didn't fully understand the nucleus's function, in 1831 he was the first to observe and describe the nucleus within plant cells, calling it the "areola" or "nucleus." His observations laid the groundwork for future research that led to the understanding of the nucleus's crucial role in cell development and heredity.

However, it was Rudolf Virchow who later proposed the famous dictum, "Omnis cellula e cellula," meaning "All cells arise from pre-existing cells." This further emphasized the importance of the nucleus in cell division and the passing on of genetic material.