Gregor Mendel conducted experiments with pea plants in the 1860s to study patterns of inheritance. Through his experiments, he discovered that inherited traits are determined by discrete units (now known as genes) that segregate and assort independently during reproduction. Mendel's work established the laws of segregation and independent assortment, which describe how traits are inherited and passed from parents to offspring through gametes and fertilization. His findings were consistent with basic rules of probability and provided evidence that supported his theories of genetic inheritance.