This is a small demonstration of inline TikZ graphics embedded directly
inside ordinary text. A simple horizontal line
\tikz \draw (0,0) -- (1,0);
can appear inside a sentence without requiring a separate figure.
We can similarly draw a small arrow
\tikz \draw[->] (0,0) -- (1,0);
or an arrow in the opposite direction
\tikz \draw[<-] (0,0) -- (1,0);
as part of the surrounding paragraph.

TikZ can also produce simple geometric objects. Here is a circle
\tikz \draw (0,0) circle (0.15);
and here is a filled circle
\tikz \fill (0,0) circle (0.12);
followed by a rectangle
\tikz \draw (0,0) rectangle (0.5,0.3);
and a filled rectangle
\tikz \fill (0,0) rectangle (0.5,0.3);.
Even a triangle
\tikz \draw (0,0) -- (0.5,0) -- (0.25,0.4) -- cycle;
can be inserted directly into the text.

Nodes are particularly useful. We can place a boxed value
\tikz \node[draw] {42};
inside a sentence, or use a circular node
\tikz \node[draw,circle] {A};
to represent a vertex. A filled node
\tikz \node[draw,circle,fill=black,text=white] {B};
could represent a black node of a red-black tree, while
\tikz \node[draw,circle,fill=red,text=white] {R};
could represent a red node.

Small mathematical diagrams can also be inserted inline. For example,
the mapping A
\tikz[baseline=-0.5ex] \draw[->] (0,0) -- (0.8,0);
B can be represented graphically rather than with an ordinary arrow.
We can make the arrow curved
\tikz[baseline=-0.5ex] \draw[->] (0,0) to[bend left] (0.8,0);
or double-headed
\tikz[baseline=-0.5ex] \draw[<->] (0,0) -- (0.8,0);
when the context calls for it.

Coordinates do not have to lie on a straight line. A tiny function-like
curve
\tikz \draw (0,0) .. controls (0.2,0.3) and (0.4,-0.3) .. (0.6,0);
can occur in ordinary prose. We can also draw two intersecting lines
\tikz {
    \draw (0,0) -- (0.5,0.3);
    \draw (0,0.3) -- (0.5,0);
}
or coordinate axes
\tikz {
    \draw[->] (-0.1,0) -- (0.6,0);
    \draw[->] (0,-0.1) -- (0,0.5);
}
without leaving the paragraph.

For data structures, suppose a node contains the value
\tikz[baseline=-0.5ex] \node[draw,circle] {8};.
Its children might be represented schematically as
\tikz[baseline=-0.5ex] {
    \node[draw,circle] (p) at (0,0) {8};
    \node[draw,circle] (l) at (-0.5,-0.6) {4};
    \node[draw,circle] (r) at (0.5,-0.6) {12};
    \draw (p) -- (l);
    \draw (p) -- (r);
}
inside the text itself. We can even show a tiny linked-list fragment
\tikz[baseline=-0.5ex] {
    \node[draw] (a) at (0,0) {1};
    \node[draw] (b) at (0.8,0) {2};
    \node[draw] (c) at (1.6,0) {3};
    \draw[->] (a) -- (b);
    \draw[->] (b) -- (c);
}
without introducing a full displayed figure.

Styling works in the short form as well. A thick line
\tikz \draw[thick] (0,0) -- (0.8,0);
a dashed line
\tikz \draw[dashed] (0,0) -- (0.8,0);
and a dotted line
\tikz \draw[dotted] (0,0) -- (0.8,0);
are all ordinary TikZ paths. Scaling the entire miniature picture is
also possible:
\tikz[scale=0.5] \draw (0,0) circle (0.5);
or
\tikz[scale=1.5] \draw (0,0) circle (0.1);.

Consequently, inline TikZ is useful for anything from tiny symbols
\tikz \fill (0,0) circle (1.5pt);
and annotations
\tikz \node[draw,rounded corners] {data};
to miniature graphs
\tikz[baseline=-0.5ex] {
    \node[circle,draw] (a) at (0,0) {};
    \node[circle,draw] (b) at (0.5,0.25) {};
    \node[circle,draw] (c) at (0.5,-0.25) {};
    \draw (a) -- (b) -- (c) -- (a);
}
embedded directly in a line of prose.