I have a layer in Illustrator with rectangular shaped picture. Basically, it is a rectangular filled with some more vectors that form the drawing.
I would like to split (or cut or divide) this rectangular and everything inside it into a mesh of smaller rectangular or squares, that I can group and separate.
In other words, I would like to take a rectangular group and divide it in pieces.
Cai’s answer works, but in some cases it mess up my artwork. Here is an example BEFORE (the cross is the grid):
Use the Rectangular Grid Tool to draw a grid over your artwork (Turning on Smart Guides may be useful to snap it easily). You can use the arrow keys on your keyboard to adjust the number of rows and columns while you drag the grid over your artwork.
Select the grid and the underlying artwork
Use the Pathfinder’s Divide command (This will create a single group from the result so you most likely want to ungroup and regroup each cell individually).
This won’t work with complex artwork though (live effects, appearance attributes etc). Outlining strokes and using “Expand Appearance” may help you out but that destructively affects your artwork so isn’t ideal.
Otherwise your only option is to use clipping masks.
Draw a rectangle over your artwork and go to Object → Path → Split Into Grid… choosing rows and columns appropriately (The rectangular grid tool creates lines but we need distinct closed rectangles to use for the clipping masks).
Select all the artwork you want to divide. Copy.
With the artwork still selected, Shift+Click a cell then create a clipping mask (cmd+7).
cmd+B to paste another copy of your artwork behind the cells and return to step 3. Repeat until finished.
Having multiple copies of the same artwork isn’t ideal so it may be an idea to create a symbol from your artwork first or use CC Library Assets.