A recent debate has been sparked about whether the Grantha characters, used to write foreign sounds ( j, ś, ṣ, s, h, kṣ ) in the Tamil script, should be included in their Unicode block.
This image is a visual overview of Grantha, compared to its related scripts used today.
Notice that the Tamil writing system contains far fewer characters, some of which are used to represent many sounds – the yellow highlighting indicates sounds traditionally represented by using the same Tamil letter. Blue highlights indicate sounds that may possibly be represented by using the equivalent Grantha character. (see “Relationship with other Indic scripts“)
Image from Wikimedia.