As default empty row/column has height/width 0 (zero) and you don't see this row/column but it exists.

import tkinter as tk

root = tk.Tk()

l1 = tk.Label(root, text='Col:8 Row:1', bg='red')
l1.grid(column=8, row=1)

l2 = tk.Label(root, text='Col:1 Row:8', bg='red')
l2.grid(column=1, row=8)

root.mainloop()

You could put Label with spaces and new lines (\n) as text

import tkinter as tk

root = tk.Tk()

l1 = tk.Label(root, text='Col:8 Row:1', bg='red')
l1.grid(column=8, row=1)

l2 = tk.Label(root, text='Col:1 Row:8', bg='red')
l2.grid(column=1, row=8)

# add empty label in row 0 and column 0
l0 = tk.Label(root, text='     \n   ', bg='green')
l0.grid(column=0, row=0)

# add empty label in row 9 and column 9
l9 = tk.Label(root, text='     ', bg='green')
l9.grid(column=9, row=9)

root.mainloop()

Or Label without text but with width/height

import tkinter as tk

root = tk.Tk()

l1 = tk.Label(root, text='Col:8 Row:1', bg='red')
l1.grid(column=8, row=1)

l2 = tk.Label(root, text='Col:1 Row:8', bg='red')
l2.grid(column=1, row=8)

# add empty label in row 0 and column 0
l0 = tk.Label(root, width=3, height=3, bg='green')
l0.grid(column=0, row=0)

l0 = tk.Label(root, width=3, height=3, bg='green')
l0.grid(column=9, row=9)

root.mainloop()

but both use width/height in chars, not pixels.

You can set minimal size for row or column (ie. row/column number 9) using

root.rowconfigure(9, minsize=30)
root.columnconfigure(9, minsize=30)

or

root.rowconfigure(9, {'minsize': 30})
root.columnconfigure(9, {'minsize': 30})

import tkinter as tk

root = tk.Tk()

l1 = tk.Label(root, text='Col:8 Row:1', bg='red')
l1.grid(column=8, row=1)

l2 = tk.Label(root, text='Col:1 Row:8', bg='red')
l2.grid(column=1, row=8)

# set minimal size for row 9 and column 9
root.rowconfigure(0, minsize=30)
root.rowconfigure(9, minsize=30)

root.columnconfigure(0, minsize=30)
root.columnconfigure(9, minsize=30)

root.mainloop()

If you like it
Buy a Coffee