He lets her guide the needle.

"It is not quite meditation? There are some mental exercises to help you connect to the crystal. And... to learn a connection, any skin part is fine, but you are going to have trouble using your biceps to manipulate the crystal as a tool."

"Yes, but that's no reason to start poking my fingertips whenever I need to be poked.  What are the exercises?"

"Focusing on the needle, focusing on your heartbeat, picturing a line or maybe your blood connecting the two... Let us do in order."

It goes on like this, various forms of visualizing and thinking of analogies for Connecting Your Life With The Crystal. Some breathing exercises. It's similar to meditation, if meditation involved more focusing on the foreign object you would normally remove. Progress comes in the form of the crystal marginally increasing in size over the course of a few minutes.

...She's actually surprisingly good at that, even after taking into account that she has relevant prior experience in guided meditations.

He remarks on this. "You are doing much better than any of us did. Do you want to try making it grow in a specific shape? Maybe we can grow it like a band around your arm."

"Yes, I think that would work.  Any specific tips, there?"

"I think it turns out smoother if we start working from the outside and inwards? And it should be a good next step exercise."

"I have no idea what you mean, so I'm just going to try this my way and see what happens."

So she will make a bracelet, taking into account what she knows of cleavage planes.

Henry shrugs and just observes. Giving pointers on how this or that process might be improved. She is good, but having any advice helps.

It certainly does, and she engages with it very well.  The bracelet she ends up with is pretty minimalist, nothing but an approximate hexagon, but she's proud of it nonetheless.

"Very well done. Do you want to learn how to crystallize existing things and then how to replicate things from crystals? Related to note: anything fragile that you own that might be good to crystalize?"

"It depends on what crystallization does to things made of e.g. mixed materials with specific properties."

"I think that most of the danger is if you're trying to use it on things that are dangerous on their own. Or if you are not skilled enough and try to use it on something alive, but that is a way ahead of ourselves."

"We'll start with something I can afford to lose, experimenting."

"Fair. Go with something of simple composition, a singular material and a single piece, then?" He then adds. "Cloth for these purposes doesn't count as a single piece."

"...hmm."

She can try...a disposable plastic mini-cup?

That works. Henry guides her like before.

It is a harder task, the goal is not just to grow the crystal, but to "push" it in a way, so it changes the substance of the cup into more crystal. It is important to also keep the information of the absorbed matter intact. Though that part is harder to get wrong with something so simple, Henry recommends train the relevant mindset.

"...like what sort of information?  Chemical composition, shape, temperature, appearance?"

"The first three, which usually means that you will get the appearance right as a consequence."

"...I'm glad this doesn't have dyes in it, then!"

She'll...try to do the thing!

It's made of hydrocarbons...She's not precisely sure which hydrocarbons...

With some Henry guidance, she gets the hang of it in no time. There is some kind of change in texture(?) inside(?) the crystal.

Though, she doesn't have enough definition to sense anything that might be hydrocarbons, she gets a vague sense of shape. It's hard to tell, but it is not hard to intuit the shape of a cup.

Yeah, the crystal has the data.  Can she make it spit the cup back out?

She can! There are ways in which, like just reversing the mental motions of crystallization. However, she loses her grasp on something. And she can feel the texture she identified as data disappearing.

This means that in a moment, she has a cup-shaped crystal attached to her bicep. Then in the next, she gets a half-crystal-half-plastic thing with another deformed half of a cup wrapped around it.

"Wow. Okay, that is... actually remarkable progress. Please check with me before doing novel things. Still, remarkable that you managed to get it at all."

"Hmm.  What sort of stuff happens if things go wrong, anyway?"

...So what if she re-crystallizes the cup, and sort of...

...Yeah, magnetic storage is a good metaphor for this...

Can she just store plastic?

"Usually you get half-destroyed things. Often the stored pattern is lost or loses some integrity such that you can't get back whatever you crystallized. Not intact, at least."

Her attempt is... something about it feels like it is failing, but failing in a way that shows that what she is trying to do is not completely wrong.