Designing Kitchens and Bathrooms - Grout Spacing

The counter top in my kitchen is 4”x 4” ceramics with 3/8” spacing for grout. I would like to replace the counter top ceramics and decrease the grout space to 1/8” or even no space for grout at all (to avoid dirt collection). My bathroom walls are also ceramics and it seems that there is no grout between the ceramics or if there is it must be less than 1/8”. My question: is it possible to install ceramics with NO GROUT between them? If I must have grout, what is the minimum distance I should allow for the grout? Thank you

You need to have a grout line. Ceramic tile has size variations that will make it next to impossible to not have a grout line. You make mention of avoiding dirt collection. The reality is there will always be some space between the tile if you have no grout line. That space will be a breading ground for dirt, grease, mold and what ever else. The size of the grout joint will depend on many things, tile size, tile size consistency, tile thickness consistency and other things. Natural stone is generally more consistent in size than ceramic and you can often get tighter grout joints with the natural stone. Its certainly possible to get 1/8" grout joints, but when you start getting smaller than that the installation gets difficult. Tile size consistency and lippage are the key issues.