Skin color in the context of Arteriole

Human variability, or human variation, is the range of possible values for any characteristic, physical or mental, of human beings.

Frequently debated areas of variability include cognitive ability, personality, physical appearance (body shape, skin color, etc.) and immunology.Variability is partly heritable and partly acquired (nature vs. nurture debate).As the human species exhibits sexual dimorphism, many traits show significant variation not just between populations but also between the sexes.

The following article lists sovereign states, dependent territories and some quasi-states according to their proportional ethnic population composition. Ethnic classifications vary from country to country and are therefore not comparable across countries. While some countries make classifications based on broad ancestry groups or characteristics such as skin color (e.g., the white ethnic category in the United States and some other countries), other countries use various ethnic, cultural, linguistic, or religious factors for classification. Ethnic groups may be subdivided into subgroups, which may or may not be identified as independent ethnic groups in their own right, depending on the source.

A number of countries also do not collect any estimates on the ethnic composition of their population (like France) and the ethnic composition of the population is of high political sensitivity in many countries, which is why reliable data are not available for many countries. Therefore, in some cases, indicators such as citizenship/nationality, ancestry or origin, country of birth, or language are used as alternative indicators. The data in the list are also of variable quality and timeliness, as only irregularly updated estimates are available for many countries. Most of the entries in the list come from the Central Intelligence Agency's World Factbook database or from national statistical offices.

Culture shock is an experience a person may have when one moves to a cultural environment which is different from one's own; it is also the personal disorientation a person may feel when experiencing an unfamiliar way of life due to immigration or a visit to a new country, a move between social environments, or simply transition to another type of life. One of the most common causes of culture shock involves individuals in a foreign environment. Culture shock can be described as consisting of at least one of four distinct phases: honeymoon, negotiation, adjustment, and adaptation.

Common problems include: information overload, language barrier, generation gap, technology gap, skill interdependence, formulation dependency, homesickness (cultural), boredom (job dependency), ethnicity, race, skin color, response ability (cultural skill set). There is no true way to entirely prevent culture shock, as individuals in any society are personally affected by cultural contrasts differently.

Melanocytes are melanin-producing neural crest-derived cells located in the bottom layer (the stratum basale) of the skin's epidermis, the middle layer of the eye (the uvea), the inner ear, vaginal epithelium, meninges, bones, and heart found in many mammals and birds. Melanin is a dark pigment primarily responsible for skin color. Once synthesized, melanin is contained in special organelles called melanosomes which can be transported to nearby keratinocytes to induce pigmentation. Thus darker skin tones have more melanosomes present than lighter skin tones. Functionally, melanin serves as protection against UV radiation. Melanocytes also have a role in the immune system.