EM --> Mech[Classical Mechanics]
EM --> Thermo[Thermodynamics \n& Fluids]
EM --> MatChem[Materials Science \n& Chemistry]
EM --> Optics[Optics \n& Waves]

%% Notice the standard HTML <span> and title tags inside the quotes!
Mech --> Norm["<span title='The fierce Coulombic repulsion between the electron clouds of the atoms of two surfaces pressed together. Nothing ever truly touches.'>Normal Force</span>"]
Mech --> Fric["<span title='Microscopic electromagnetic bonds constantly forming, snapping, and reforming between the irregular atomic topographies of sliding surfaces.'>Friction</span>"]
Mech --> Tens["<span title='The macroscopic sum of electromagnetic bonds between atoms resisting being stretched apart from their equilibrium distance.'>Tension & Elasticity</span>"]
Mech --> Visc["<span title='Electromagnetic interactions between sliding layers of fluid molecules that resist relative motion, causing internal friction.'>Viscosity & Drag</span>"]

Thermo --> Phase["<span title='Latent heat is simply the exact energy required to overcome or form electromagnetic dipole-dipole attractions (like hydrogen bonds) holding molecules together.'>Phase Transitions</span>"]
Thermo --> Kinetic["<span title='Gas molecules in a container never physically collide like billiard balls; their electron shells repel each other electromagnetically, causing them to scatter.'>Kinetic Gas Collisions</span>"]

MatChem --> Lattice["<span title='Whether a material is brittle or ductile depends on the precise arrangement of atoms that minimizes the total electrostatic potential energy of the system.'>Crystal Lattices</span>"]
MatChem --> Bonds["<span title='Covalent, ionic, and metallic bonds are purely electromagnetic interactions—finding the most stable configuration of nuclei and electron clouds.'>Chemical Bonding</span>"]
MatChem --> Semi["<span title='The foundation of computing: electrons navigating the complex, periodic electromagnetic potential wells of a crystal lattice.'>Semiconductor Bands</span>"]

Optics --> Light["<span title='Maxwells revelation: Optics is just electromagnetism. Light is a self-propagating wave of oscillating electric and magnetic fields.'>The Nature of Light</span>"]
Optics --> Refract["<span title='The interaction of incoming electromagnetic light waves with the electron clouds of a material, which slows the waves phase velocity.'>Refraction & Dispersion</span>"]

`}