slicing and indexing a list example

[leodavinci1990]

I have the following code:

s = "The quick brown fox jumps over the lazy dog."
words = s.split()
lengths = [[w.lower(), len(w)] for w in words]
for length in lengths:
 print(length)

The output is:

['the', 3]
['quick', 5]
['brown', 5]
['fox', 3]
['jumps', 5]
['over', 4]
etc.

I wish to change it to produce the lengths only, namely the numbers.
Also, is this an example of lists inside lists (nested lists)?
I am trying to