Heredity is the passing of traits to offspring (from its parent or ancestors). This is the process by which an offspring cell or organism acquires or becomes predisposed to the characteristics of its parent cell or organism. Through heredity, variations exhibited by individuals can accumulate and cause some species to evolve. The study of heredity in biology is called genetics, which includes the field of epigenetics.

In humans, eye color is an inherited characteristic and an individual might inherit the "brown-eye trait" from one of the parents. Inherited traits are controlled by genes and the complete set of genes within an organism's genome is called its genotype.

The complete set of observable traits that make the structure and behavior of an organism is called its phenotype. These traits come from the interaction of its genotype with the environment. As a result, many aspects of an organism's phenotype are not inherited. For example, suntanned skin comes from the interaction between a person's genotype and sunlight; thus, suntans are not passed on to people's children. However, some people tan more easily than others, due to differences in their genotype; a striking example are people with the inherited trait of albinism, who do not tan at all and are very sensitive to sunburn.

Gregor Johann Mendel (July 20, 1822 – January 6, 1884) was an Austrian scientist and Augustinian friar who gained posthumous fame as the founder of the new science of genetics. Mendel demonstrated that the inheritance of certain traits in pea plants follows particular patterns, now referred to as the laws of Mendelian inheritance. Although the significance of Mendel's work was not recognized until the turn of the 20th century, the independent rediscovery of these laws formed the foundation of the modern science of genetics.

Mendel was born into an ethnic German family in Heinzendorf bei Odrau, Austrian Silesia, Austrian Empire (now Hynčice, Czech Republic), and was baptized two days later as Johann. He was the son of Anton and Rosine (Schwirtlich) Mendel, and had one older sister (Veronica) and one younger (Theresia). They lived and worked on a farm which had been owned by the Mendel family for at least 130 years. During his childhood, Mendel worked as a gardener, studied beekeeping, and as a young man attended Gymnasium (school) in Opava. From 1840 to 1843, he studied practical and theoretical philosophy as well as physics at the University of Olomouc Faculty of Philosophy, taking a year off because of illness.