dainty, get thin, taper, slender, narrow, detailed, precise
細 centers on thinness and fineness: something slender, narrow, or delicate, and by extension, something detailed or precise because it has been broken down into fine parts.
細 combines 糸 (thread) and 田 (field), but the 田 here is likely a simplified or stylized form of a component suggesting smallness or division. The character expresses the idea of something as fine as thread.
Picture a thin thread 糸 being woven through a tiny field 田 of fabric, making the weave fine and detailed.
For サイ, imagine a sigh of relief when you finally thread the needle: sigh -> サイ, and the thread is so slender and precise.
details; particulars; specifics
cell
small
thin; slender; fine
bacterium; bacteria; germ
dainty; delicate (e.g. fingers); fine; slim
trivial; trifling; slight; insignificant
small; fine; detailed; stingy
work; workmanship; craftsmanship; handiwork
details; particulars
small; little; tiny; insignificant; humble; modest; meagre; meager
details; particulars; specifics
subdivision (into small parts)
long and narrow
minute; fine; detailed; subtle
poor (living)
minutely; in detail; with particular attention
meticulous; careful; discreet; scrupulous; prudent
insignificant; trifling; paltry; cottage (industry); tiny (company)
helpless; forlorn; hopeless; unpromising; lonely; discouraging; disheartening
particulars; details; specified items
to get thin; to taper off
trifles; minor details
minutely; finely
inside the cell; intracellular