Step 1: Selection of pea plants: Mendel selected pea plants (Pisum sativum) as his model organism because they had several distinct and easily observable traits, such as flower color, seed shape, and plant height. He chose pea plants that were true-breeding, meaning they always produced offspring with the same traits as themselves.

Step 2: Cross-pollination and generation analysis: Mendel conducted controlled crosses between different pea plants to study the inheritance of specific traits. He used two methods of crosses:

- Monohybrid cross: Mendel crossed pea plants that differed in one specific trait, such as flower color (white vs. purple). He observed the resulting offspring (F1 generation) and then allowed them to self-pollinate to obtain the second generation (F2 generation).

- Dihybrid cross: Mendel also performed crosses involving two different traits, such as flower color and seed shape. He observed the inheritance of both traits in the F1 and F2 generations.

Step 3: Data analysis and formulation of laws: Mendel carefully recorded his observations and analyzed the data he obtained from his experiments. He used mathematical ratios to describe the patterns of inheritance and formulated his principles of heredity, known as Mendel's laws:

- Law of segregation: During gamete formation (pollen and eggs), the alleles for a gene separate (segregate) and randomly combine with alleles from the other parent during fertilization.

- Law of independent assortment: The alleles of different genes assort independently of one another during gamete formation, resulting in new combinations of traits in offspring.

These three steps allowed Mendel to establish the fundamental principles of inheritance, which laid the foundation for modern genetics.