1. Emergency medicine Sports medicine

Sports medicine is a branch of medicine that deals with physical fitness and the treatment and prevention of injuries related to sports and exercise. Although most sports teams have employed team physicians for many years, it is only since the late 20th century that sports medicine has emerged as a distinct field of health care. In some countries, Sports medicine (or Sport and Exercise medicine) is a recognized medical specialty (with similar training and standards to other medical specialties), whereas in other countries it is a special interest area but not an actual specialty.
Sports medicine can refer to the specific medical specialty or subspecialty of Sports Medicines. Sport and Exercise Medicine (SEM), which is now well established in many countries. 
SEM consultants also deliver clinical physical activity interventions, negating the burden of disease directly attributable to physical inactivity and the compelling evidence for the effectiveness of exercise in the primary, secondary and tertiary prevention of disease.
European templates for SEM specialisation generally recommend 4 years of specialist training in all of:

• 
  internal medicine with special emphasis on cardiology, emergency medicine and clinical nutrition
  
• 
  orthopaedics and traumatology
  
• 
  physical and rehabilitation medicine
  
• 
  fellowship at a recognised sports medicine centre.
  

3. World Health Organization

The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health.^[1] The WHO Constitution, which establishes the agency's governing structure and principles, states its main objective as "the attainment by all peoples of the highest possible level of health."^[2] It is headquartered in Geneva, Switzerland, with six semi-autonomous regional offices and 150 field offices worldwide.
The WHO was established by constitution on 7 April 1948,^[3] which is commemorated as World Health Day.^[4] The first meeting of the World Health Assembly (WHA), the agency's governing body, took place on 24 July 1948. The WHO incorporated the assets, personnel, and duties of the League of Nations' Health Organisation and the Office International d'Hygiène Publique, including the International Classification of Diseases (ICD).^[5] Its work began in earnest in 1951 following a significant infusion of financial and technical resources.
The WHA, composed of representatives from all 194 member states, serves as the agency's supreme decision-making body. It also elects and advises an executive board made up of 34 health specialists. The WHA convenes annually and is responsible for selecting the director-general, setting goals and priorities, and approving the WHO's budget and activities. The current director-general is Tedros Adhanom, former health minister and foreign minister of Ethiopia, who began his five-year term on 1 July 2017.

4. A field of medicine you want to choose – Neurosurgery