adding lists to lists?

[ivinjjunior]

hey everyone, i'm new in coding and i really need to create logic to help me in my job..
i am having trouble with creating a way to put lists into a existing one.. for example, i would like to make a input generate a list..

ex:
itens = []
itens.append(A)

i want this letter A to be placed into the list itens like this:

[[a]]

if i want to append a new letter it would generate a new list..

[[A], [B]]

is this even possible? it would be less complex to achieve what i need this way..