White Hairs On Kids And Teens

This is happening nowadays. 

Kids and teens already have white hairs
or gray hairs on their heads
like those you find in old people. 
How come?

This teen is still 13 years old, but his black hair is tainted with white hairs already.

This is kind of alarming for me
especially when I don't have white hairs
when I was a kid and in my teens.
What could possibly be the cause of this?
Is it the food?
Is it the technological advancements that they are exposed to,
like computers, tablets and smartphones?
​Or is the result of climate change or global warming? 
​
White hairs are supposed to be signs of wisdom and old age,
but with kids and teens,
wisdom and old age ​don't really apply.

This girl is still not in her teens, but white hairs are showing on her head.

Kids and teens learn faster nowadays
and easily adopt to new environments.
They are the new and younger generation
who are considered better and wiser than the previous ones. 

But having white hairs at their age 
is hard to equate to being better and wiser 
because they still lack exploration and experience. 

Kids and teens who have white hairs 
don't feel comfortable about them
and even feel embarrassed
because they look much older than their age.

I still remember my grandpa when he was still alive and active
sporting a black shiny hair all his life even at past 60.
Not one of his hair was gray or white.
I wonder why he got black hair up to the day he died
when he was not using dye.

Kids and teens who got white hairs
and an old man who never had any until the day he died  
are equally perplexing ​and bewildering to me. 

As I browse the web, 
I can't find any reliable explanation on having gray or white hairs; 
why they're there in the first place. 
There's still so much about us that we know nothing about 
that still needs to be studied over the years. 
​
Our knowledge is just too little, 
like a single drop of water in the ocean 
​or a single grain of sand on the seashore.