The guts of the new phone look very similar to last year's iPhone X. One of the most interesting features is the battery on the XS. The iPhone XS sports a slightly downgraded battery from the iPhone X, a 10.13 Wh battery (2,659 mAh at 3.81 V) versus 10.35 Wh (2716 mAh at 3.81 V). But a new configuration might more than make up for it: Apple is using a brand-new L-shaped single-cell battery instead of two separate batteries. However, the XS Max still sports two batteries.
For the full teardown, hop on over to iFixit's post on both the XS and XS Max to see what the internals of these phones look like for yourself.