Chicken farming started small. This is called a family farm. Because chicken is very useful, families had several chicken. They gave them eggs and they could hatch more chickens. Today, we eat chicken all the time. This was not the habit before the 20th century. Chickens were used mostly for eggs and trade. This means that people on family farms collected eggs and traded them for money or something else useful. Bartering chicken eggs is as old as our civilization. In addition, people did not eat as much chicken. Usually, this was a special occasion or Sunday meal. Often, people only ate roosters that were not needed or the hens that did not make enough eggs. Because these birds were not useful any more, they were the first to be eaten and butchered. Chicken on small farm in Croatia The small family farms became larger when cities started to be built. People in cities usually did not have space for raising chicken. But, they still wanted meat and eggs. People in rural areas soon figured out this will be a good source of income. They added few more chicken to their farms. This way they produced more eggs and meat. They kept some for themselves and their family, and took the excess to the farmers markets. These kinds of markets still exist worldwide and many small farmers bring their goods. Many people enjoy buying the goods from the small farms because they are fresh or organic products. Until the cases of Avian Flu, farmer's market was a great place to buy fresh eggs and chicken. Since Avian Flu was found this is not allowed. Only packaged products are found. This could really hurt people who brought their product to the market to make living. \One of the reason people raised chicken is the meat and eggs. The other is that chicken are not very difficult to raise.  It is also not too expensive. One of the things common on chicken farms are chicken coops. These are the barns that house chicken. Chicken coops provide necessary shelter from weather issues such as cold or heat. Chicken coops were usually constructed from wood and layered with hay, so that chicken can get warmer and have place to lay their eggs. The biggest cost in raising chickens is the chicken feed. Today we have many brands of chicken feed that assure that our chicken are getting proper nutrition, produce eggs and have enough meat. But hundred years ago, commercial chicken feed was rarely used on family farms. Instead , chicken were fed pastured grass or bread crumbs. Pasture grass was good for chicken because it provided good nutrition as well as insects that chicken could eat. In addition to grass, chicken were given table scarps of bread crumbs or corn to supplement what they got from the grass. This worked well for the small family farms, but not for large commercial farms. Chicken on this Croatian farm often eat grass The biggest change in the world of chicken farming was definitely the invention of refrigeration. One of the problems that small family farmers faced was that eggs and chicken meat spoiled quickly and could cause diseases such as salmonella. They could not take their product very far and they had to sell it all at once. The product that was not sold in the day on the farmers market had to be thrown away because it could have been spoiled. This all changed with the invention of refrigeration Refrigeration means to cool down.  When you lower the temperature of eggs or chicken meat,  bacteria cannot grow as fast as in normal temperature. That meant that eggs and meat could last longer and farmers could sell them in the places further away or the next day.  While use of refrigeration was known to people for centuries (for example people in the North used snow and natural ice to preserve food), it was the invention of the refrigerator that changed the chicken industry. Refrigerator is a common kitchen appliance that is used to preserve food by cooling it down. In addition to cooling, many refrigerators have compartments for freezing. Freezing preserves food for even longer times. The very first real refrigerator was created in 1856 and by 1957 people invented trains with refrigerated cars. The chicken farming changed forever. Suddenly, people could raise thousands of chicken and collect thousands of eggs and transport them to markets far away. This meant the end of the small family farm. While in some places in the world and some rural area there are still small family chicken farms that support families, they have now mostly been replaced with a large commercial farms. These large farms supply grocery chains and restaurants and bring chicken products to our table.