Space of germs of holomorphic functions
= Space of germs of holomorphic functions
The space $\mathcal G$ of germs over a domain $D$ has basic open sheets
$$
\{[f]_z:z\in U\}
$$
for holomorphic $f$ on open $U\subseteq D$. The projection $\pi([f]_z)=z$ restricts to a homeomorphism on each sheet, and these projections form holomorphic coordinate charts.