Dhātu-vavatthāna: The comprehension of dhātus

At an instant in a form object or any real object

All the four dhātus, i.e. all the four states of matter

The paṭhavi dhātu as solid, the āpo dhātu as liquid

The vāyo dhātu as gas, and tejo dhātu as heat

At the novice level, states of matter as dhātus

But for higher stages more subtle lakkhaṇa (properties) of matter

Rather than just paṭhavi as solid, more precise, i.e., degree of hardness and softness

Āpo as the degree of fluidity and cohesion

Vāyo as the motion, vibration, support

Tejo as the degree of hotness and coldness

Because at characteristic level, dhātus, not just conceptual categories

Instead, direct objects for senses

Shifting of attention from coarse dhātu to subtle lakkhaṇa

May or may not the noting method shift from continuous to transition basis of noting

Continuous noting vs transition basis of noting

Continuous noting when continuous noting of any dhātu in mind

Like whilst a walk, vāyo dhātu, vāyo dhātu, ...

Transition basis of noting when noting of a dhātu only on switching

Like when switching over of focus from vāyo dhātu to tejo dhātu, and so on

Continuous noting suitable for a novice, for a beginner

Suitable for upaṭṭhāna (stable presence with the object) 

Transition basis noting in some higher stage

For sharpening of udayabbaya discrimination (the arising/passing at boundaries)