How Many Categories Of Nobel Prize Are There?

Until 1991 there were 7 categories of Nobel prizes.  These were physics, chemistry, physiology & medicine, literature, peace and economics.  These (apart from economics which was introduced in 1969) were all established in 1901.

However, in 1991, several other categories have been introduced and awards have been presented for public health, engineering, biology and inter-disciplinary research.

The peace and literature awards are generally the most famous.  Awards are not made every year, for example, during the First World War, 1914 ~ 1918 only one peace award was made, to the International Red Cross Committee, which had been established in 1863.

Similarly during the Second World War the International Red Cross Committee were awarded the single peace award made during the war.  

Perhaps the most controversial of the peace awards was Henry Kissenger being awarded the Peace Prize for his work trying to resolve the Middle East crisis.  He was given the award in 1973.  The other person who was awarded the Peace Prize in that year was Le Duc Theo.  He declined the award, apparently in protest over Kissenger's award.