(History)
The bathroom for washing is recorded as far back as 5,000 years ago as well as early Egyptian/Greece & Rome:

Washing except for the hands & face was unpopular in the Middle Ages: In the 1600's/1700's, many thought it unhealthy: In early 1800's, baths & bathing came into fashion and most substantial houses of this period had bathrooms. The toilet (non-plumbing varieties) also has a long history: in general, the necessary function was done outdoors, away from the house: Chamber pots & outdoor Latrines was the American answer: In the late 1800's, a version of a "water closet" was invented by Thomas Clapper and the bathroom as we know it today, came into existence.

The bathroom today has continued to grow in size & splendor: it has become a major selling point and can influence selling or buying homes/renting apartments: how many? layout/family size and habits should be taken into consideration: the bathroom/bathrooms require the most heat and ventilation of any room in the house: lighting is important: accessories and storage/counter surfaces/full length mirrors/ample towel bars/shelving are just SOME of the features to be considered: Jacuzzi's/Saunas/and room for excerise equipment are special options should you really want to "customize":