Origin: It is believed that yogurt originated in Turkey, and the word comes from the verb "yogurmak" which means to thicken. The history of yogurt dates back to the 6th century BCE in Turkey.
Most historical accounts attribute yogurt to the Neolithic peoples of Central Asia around 6000 B.C. It is believed that Herdsmen began the practice of milking their animals, and the natural enzymes in the carrying containers curdled the milk, essentially making yogurt. It was then believed that people started preferring the taste so continued the practice of making yogurt, which later evolved over centuries into the commercial yogurt making process

The reason for the yogurt to have good bacteria was that it bloomed when the milk interacted with the animal stomach bags. This made the curdled liquid a hostile environment for bad bacteria to grow.

In many ancient Asian civilizations, yogurt was a part of their daily diet. Many Mughal emperors like Genghis Khan and his Mongol army devoured the taste of yogurt. It was also believed that yogurt provided them with strength and stamina. Even the Indian emperor Akbar enjoyed yogurt with spices like cinnamon, cumin powder, and mustard seeds. 
The first industrialized production of yogurt was done by Isaac Carasso in 1919 in Barcelona under his company “Danone''.

It is believed that the Turkish immigrants brought yogurt to North America in the late 1700s but it really didn’t catch the attention until the 1940s.  The founder of Danone Isaac and Juan Metzger took over a small yogurt factory in the Bronx, New York – the company is now called Dannon in the United States.

The new variant of Yogurt with fruit on the bottom was first introduced in 1947 by Dannon.
The popularity of yogurt increased in the 50s and 60s with the boom of the health food culture and is now available in many varieties to suit every taste.

Scientifically: Yogurt is made by combining milk with bacteria (also known as a yogurt starter culture) and letting it culture. Today, the FDA defines yogurt as a milk product fermented by two bacterial strains: a lactic acid-producing bacteria: Lactobacillus bulgaricus and Streptococcus thermophiles.

How to make the Yogurt: To make yogurt, milk is first heated to 180 degrees Fahrenheit for 30 minutes to denature the whey proteins. This allows the proteins to form a more stable gel in the yogurt. The yogurt is pasteurized before adding the cultures. The pasteurization process kills any pathogens in it that can spoil milk. After milk pasteurization, the milk is cooled down to 108 degrees Fahrenheit, the temperature for optimal growth of yogurt starter cultures. Last, the yogurt starter cultures (probiotics) is added into the cooled milk and incubated until a pH of below 5 is obtained. This is called the fermentation process, whereby lactose in the milk is converted to lactic acid, which lowers the pH. The denatured casein proteins reassemble by interacting with other casein proteins, and this result in a network of molecules that provides the semisolid texture of yogurt.

The fermentation process is also essential for the tangy flavor of yogurt: the production of lactic acid by Lactobacillus bulgaricus imparts a sour acidic and refreshing taste. 

Usage: Yogurt is used to make various savory and sweet dishes, smoothies, shakes, etc.  Yogurt is also used for constipation, treating and preventing vaginal yeast and bacterial infections, and it also prevents urinary tract infections. Some people use yogurt for lactose intolerance and for treating high cholesterol, diabetes. 

Below are some DIYs for beautiful skin and hair:

-    Take 3 tablespoons of yogurt, 1 tablespoon of cocoa powder and 1 teaspoon of honey. Combine all the ingredients together and apply on the face for 15 minutes. Gently massage and rinse it off. This moisturizes the skin.
-    Take 2 tablespoons of yogurt and a tablespoon of oats. Mix them together and apply on the face. Rinse after 10 minutes. This helps in removing the dead skin and gives radiant skin.
-    Yogurt is effective in reducing acne. Take some yogurt and apply on the affected areas. This helps in reducing the appearance of the acne.
-    Take a tablespoon of yogurt and add some lemon juice to it. Mix together and apply on the face for 15 minutes. This helps in reducing acne scars and pigmentation.
-    Make a nourishing hair pack at home with a cup of yogurt. Add some fresh aloe vera gel and some coconut oil to it. Combine all the ingredients together and apply on the scalp and hair for 45 minutes. Shampoo as usual. This helps in conditioning the hair and makes them more manageable. 
-    Take half a cup of yogurt with 3 tablespoons of fenugreek seeds. Blend them together and apply on the hair. Shampoo after 30 minutes. This hair pack helps in reducing hair fall.