fig-sharing.tex

\documentclass[tikz,border=7pt]{standalone}
\usepackage[T1]{fontenc}
\usepackage{lmodern,amsmath,amssymb}
\hyphenpenalty=10000
\exhyphenpenalty=10000
\usetikzlibrary{arrows.meta,positioning,calc,fit,backgrounds}
\definecolor{ink}{HTML}{243B4A}
\definecolor{pale}{HTML}{EFF5F7}
\definecolor{warm}{HTML}{FAF5E8}
\tikzset{every node/.style={font=\sffamily\small,text=ink},
 box/.style={draw=ink!65,rounded corners=2pt,fill=pale,align=center,inner sep=7pt},
 warmbox/.style={box,fill=warm},
 arr/.style={-{Latex[length=2mm]},draw=ink!80,line width=.65pt},
 lab/.style={font=\sffamily\footnotesize,fill=white,inner sep=2pt},
 dot/.style={circle,draw=ink!75,fill=white,minimum size=8mm,inner sep=1pt},
 title/.style={font=\sffamily\bfseries\small,align=center}}
\begin{document}\begin{tikzpicture}

\node[box] (old) at (0,0) {old root};\node[box] (new) at (0,2) {new root};
\node[box,minimum width=1.5cm] (y) at (3.1,2) {$y$};
\node[box,minimum width=1.5cm] (x1) at (6.2,0) {$x_1$};
\node[box,minimum width=1.5cm] (x2) at (9,0) {$x_2$};
\node[box,minimum width=1.5cm] (x3) at (11.8,0) {$x_3$};
\draw[arr] (new)--(y);\draw[arr] (old)--(x1);\draw[arr] (y.south east)--(x1.north west);
\draw[arr] (x1)--(x2);\draw[arr] (x2)--(x3);\draw[arr] (x3)--++(1,0)node[right]{$\varnothing$};
\node[align=center] at (8.5,1.9) {One new cell; the old tail is shared.\\Both roots retain their meanings.};

\end{tikzpicture}\end{document}