Availability for emergency
No matter how beautiful your tile is, if the grout is in bad shape it can make your bathroom look like it belongs in a 1950s motel. Most of the time, killing mildew and resealing the grout will cure the problem. But if the mildew persists or the grout is really shot, or if the grout has succumbed to the ravages of time and moisture, or if the grout is hopelessly stained, crumbling or missing between tiles making it look bad, allowing water, dirt and debris to accumulate and even damage the tile substrate. then it's time to re-grout! Re-grouting is the only way your tiles can look new again when the grout is severely damaged. Another reason to re-grout is to change to a different grout color when 
Grout is a construction material used to embed rebars in masonry walls, connect sections of pre-cast concrete, which fills in the cracks between tiles, keeping them together and preventing damage to the sides of the tiles. Grout is generally composed of a mixture of water, cement, sand, often color tint, and sometimes fine gravel (if it is being used to fill the cores of cement blocks). It is applied as a thick liquid and hardens over time, much like mortar.
Main varieties include urethane, cement-based or epoxy grout. There are a few tools associated with applying and removal of grout such as:
- Grout saw or grout scraper; a manual tool for removal of old and discolored grout.
- Grout float; A trowel-like tool for smoothing the surface of a grout line, typically made of rubber or soft plastic.
- Dremel grout attachment; an attachment guide used in a die grinder for faster removal of old grout than a standard grout saw.
- Grout sealer is a water based or solvent based sealant applied over dried grout that resists water, oil, and acid-based contaminants.
With time, grout can get dirty, especially the grout used around kitchen and bathroom tiles which are exposed to food, soaps, and lots of water. It is relatively easy to clean tile grout, especially when it is regularly maintained.