Iotation can result in a partial palatalization so the centre of the tongue is raised during, and sometimes after, the articulation of the consonant.
This table summarizes the typical outcomes in the modern Slavic languages: According to most scholars, the period of iotation started approximately in the 5th century, in the era of Proto-Slavic, and it lasted for several centuries, probably into the late Common Slavic dialect differentiation.
As a result of the phenomenon, no native Slavic root starts with an [e] or an [a] but only with a [je] and [ja]; although other vowels are possible.
As it was invented for the writing of Slavic languages, the original Cyrillic alphabet has relatively complex ways for representing iotation by devoting an entire class of letters to deal with the issue.
There are also two special letters (soft sign Ь and hard sign Ъ) that also induce iotation; in addition, Ь palatalizes preceding consonant, allowing combinations of both palatalized (soft) and plain (hard) consonants with [j].
When Vuk Karadžić reformed the Serbian language, he created new letters to represent iotated consonants.