Question: *Part of the [everyday object series](https://puzzling.stackexchange.com/search?q=body%3A%22everyday+object+series%22+is%3Aquestion)*

> 
> I present to you: the everyday fay.  
> 
>  Its ancestor was born on the very first day.  
> 
>  It lives alone, but can work well in a team,  
> 
>  Only comes alive when its foot is engulfed in a stream.  
> 
>  Its head is what's most important to us,  
> 
>  The material therein is almost superfluous;  
> 
>  That which comes out, that is the prize.  
> 
>  Incorporeal, yet it made us modernize.
> 
> 
> 

What is this everyday fay?

Answer: 
I believe this is

> 
>  A lightbulb
> 
> 
> 

Its ancestor was born on the very first day.

> 
>  The sun, our world’s original light source
> 
> 
> 

It lives alone, but can work well in a team,

> 
>  One bulb per socket, but multi-socket fixtures provide more light
> 
> 
> 

Only comes alive when its foot is engulfed in a stream.

> 
>  A “stream” of electricity 
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> 
> 

Its head is what's most important to us,

> 
>  As that’s where the light comes from
> 
> 
> 

The material therein is almost superfluous;

> 
>  Light bulbs are basically vacuums inside, other than the slenderest filament
> 
> 
> 

That which comes out, that is the prize.

> 
>  The light, of course. 
> 
> 
> 

Incorporeal, yet it made us modernize.

> 
>  The light bulb spurred electric power distribution grids and all that came with ready availability of electricity to households. 
> 
> 
>
It sounds like a

> 
>  transistor
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> 
> 

I present to you: the everyday fay.
Its ancestor was born on the very first day.

> 
>  perhaps this references the electron?
> 
> 
> 

It lives alone, but can work well in a team,

> 
>  A transistor is standalone, but works well in a circuit
> 
> 
> 

Only comes alive when its foot is engulfed in a stream.

> 
>  I think this refers to the need of current (a stream of electrons) for it to operate
> 
> 
> 

Its head is what's most important to us,
The material therein is almost superfluous;

> 
>  the material of a transistor can vary, but doesn't affect how it works
> 
> 
> 

That which comes out, that is the prize.
Incorporeal, yet it made us modernize.

> 
>  We are modernized because of the transistor
> 
> 
>