Wilhelm Johannsen was a Danish botanist and geneticist born on February 3, 1857. He is best known for his work in the field of genetics, particularly for introducing the terms genotype and phenotype. Johannsen's research helped to clarify the distinction between an organism's genetic makeup and its observable traits. In 1903, Johannsen conducted experiments with beans that demonstrated how traits are inherited. His findings laid the groundwork for modern genetics and influenced future scientists, including Gregor Mendel, whose earlier work on inheritance patterns Johannsen helped to popularize. Johannsen passed away on December 11, 1927.