The Cajal (coiled) body is a discrete nuclear organelle that was first described 
in mammalian neurons in 1903. Because the molecular composition, structure, and 
function of Cajal bodies were unknown, these enigmatic structures were largely 
ignored for most of the last century. The Cajal body has now regained the 
interest of biologists, due to the isolation of a protein marker, coilin. 
Despite current widespread use of coilin to identify Cajal bodies in various 
cell types, its structure and function are still little understood. Here, I 
would like to discuss what we have learned about coilin and suggest a possible 
role for coilin in RNA processing and cellular trafficking, especially in 
relation to Cajal bodies and nucleoli. Although coilin has been investigated 
primarily in somatic cells, I will emphasize the advantages of using the 
amphibian oocyte to study nuclear proteins and organelles.