Clara cells are dome-shaped cells

Cell (biology)

The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....

 with short microvilli found in the small airways (bronchioles) of the lung

Lung

The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...

s.
Clara cells are found in the ciliated simple epithelium. These cells may secrete glycosaminoglycans

Glycosaminoglycan

Glycosaminoglycans or mucopolysaccharides are long unbranched polysaccharides consisting of a repeating disaccharide unit. The repeating unit consists of a hexose or a hexuronic acid, linked to a hexosamine .-Production:Protein cores made in the rough endoplasmic reticulum are posttranslationally...

 to protect the bronchiole lining.Bronchiolar cells gradually increase in number as the number of goblet cells decrease.

They are also known as "bronchiolar exocrine cells".
"Clara cells" were originally described by their namesake, Max Clara

Max Clara

Max Clara was an Austrian anatomist. He was appointed as Chair of Anatomy at Leipzig University in 1935. Clara is known for having close ties with the Nazi Party, basing much of his controversial work on his studies of the bodies of executed prisoners...

 in 1937.