Multistep Registration Form while googling and reading documentation and API, I've seen multiple solutions for "combining" 2 forms into one, and thus creating a multistep form.

What I want though, not even sure if it's doable, is to "split" my (huge) user registration form into 2 steps, where the value of one field (the only one in step 1) would determine which fields should show up in step 2.

I wouldn't like to drop the entire registration form and re-create it in code or in another way and somehow re-implement the whole user registration process. Is that possible?

EDIT: to avoid misunderstandings, what I need to do is an "actual" multistep form, with submitions between steps, and not some front-end handling. That is, I want the whole thing to be javascript independant.

EDIT2: to clarify even further, the task is figure out how/if possible to pretty much split any "edit" form to 2 parts. The current question does ask about the user/edit and/or user/register form specifically, but in order to come up with a more generalized solution, one might also want to split a node/edit form in to 2 parts. That's what I am really asking about. Splitting an entity/edit form in to 2 (or more) steps.
One way to do this would be to use the Conditional Fields module (disclaimer: noted as not ready for production for D7).  The way to do it with your own code would be to use the States API (the Conditional Fields module is just a GUI to States API, basically).

Using Conditional Fields, you can set it so that, for example, based on the value selected for Field A, a number of fields would be shown or not shown as per your requirements. 

EDIT: To split the form into two steps, you can use the Field Group module, which provides a "multipage steps" feature.  To configure this, you will need to create a fieldgroup of type multipage for each page you want to have on the user registration form, and then place the appropriate fields under each page (on the user account manage fields screen).

Note: The Conditional Fields and Field Group module will display everything as one giant page if Javascript is disabled.  I don't know any way around this.