How to fix Stack Overflow on a simple script?

Hi! I'm New to LUA! I've been playing around with FOR.

==[What does the script do?]== When I enter stuff on the TextBox, it slowly types it in the TextLabel.

Here's the object Tree https://gyazo.com/931c9ff84ad0eba39d17955f9b5a673f

Script in textbox.

local scroll = script.Parent.Parent:WaitForChild("Main")
script.Parent.FocusLost:connect(function(enterPressed)
	if enterPressed then
		Echo(script.Parent.Text)

	end
end)



function Echo(word)
	Echo(script.Parent.Text)
	for i=1,string.len(word) do
		scroll.Text=string.sub(word,1,i)
		wait(.05)
	end
		
	wait(2)
	scroll.Text=""
end

It gives me: https://gyazo.com/c7429d99ab6ebb79ab897c63af8ad598 Stack Overflow. I never encounted this problem before, I have no idea how to fix it. @koolkid8099 told me "It's when a program tries to use more memory, than available."