  Let $G$ be a simple finite graph and $G'$ be a subgraph of $G$. A $G'$-design
$(X,\cal B)$ of order $n$ is said to be embedded into a $G$-design $(X\cup
U,\cal C)$ of order $n+u$, if there is an injective function $f:\cal
B\rightarrow \cal C$ such that $B$ is a subgraph of $f(B)$ for every $B\in\cal
B$. The function $f$ is called an embedding of $(X,\cal B)$ into $(X\cup U,\cal
C)$. If $u$ attains the minimum possible value, then $f$ is a minimum
embedding. Here, by means of K\"{o}nig's Line Coloring Theorem and edge
coloring properties a complete solution is given to the problem of determining
a minimum embedding of any $K_3$-design (well-known as Steiner Triple System
or, shortly, STS) into a 3-sun system or, shortly, a 3SS (i.e., a $G$-design
where $G$ is a graph on six vertices consisting of a triangle with three
pendant edges which form a 1-factor).
