Apple Watch Series 4 brings a lot of changes, but how much has it changed on the inside? Quite a bit, actually -- iFixit has torn down the new smartwatch, and it's clear that this was Apple's opportunity to rethink some of the hidden details. For one, it offers a good look at Series 4's ECG monitoring, including the components in the Digital Crown that complete the circuit. You'll also see a much thinner (if longer) Taptic Engine, a much larger speaker and a smaller battery -- the 44mm Watch pack has 20 percent less capacity than that from the 42mm Series 3. Apple may be counting on the newer processor and other refinements to make up the difference.