diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index fbbd2ee2..2b9690a7 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -17,7 +17,7 @@ repos:
         types_or: [python, jupyter]
 
   - repo: https://github.com/pre-commit/mirrors-mypy
-    rev: v1.13.0
+    rev: v1.14.0
     hooks:
       - id: mypy
         additional_dependencies: [types-requests, types-PyYAML]
diff --git a/pymatviz/enums.py b/pymatviz/enums.py
index 2468b39b..dc91610a 100644
--- a/pymatviz/enums.py
+++ b/pymatviz/enums.py
@@ -152,8 +152,78 @@ def label(self) -> str:
 
     @property
     def unit(self) -> str | None:
-        """Unit associated with the key."""
-        return _keys[self.value].get("unit")
+        """Unit associated with the key with HTML tags for sub/superscripts."""
+        if not (unit := _keys[self.value].get("unit")):
+            return None
+
+        # Map Unicode characters to their ASCII equivalents
+        superscript_map = {
+            "⁰": "0",
+            "¹": "1",
+            "²": "2",
+            "³": "3",
+            "⁴": "4",
+            "⁵": "5",
+            "⁶": "6",
+            "⁷": "7",
+            "⁸": "8",
+            "⁹": "9",
+            "⁻": "-",
+            "½": "1/2",
+        }
+        subscript_map = {
+            "₀": "0",
+            "₁": "1",
+            "₂": "2",
+            "₃": "3",
+            "₄": "4",
+            "₅": "5",
+            "₆": "6",
+            "₇": "7",
+            "₈": "8",
+            "₉": "9",
+            "₋": "-",
+            "½": "1/2",
+        }
+
+        # Process character by character
+        html_str = ""
+        in_super = in_sub = False
+
+        idx = 0
+        while idx < len(unit):
+            char = unit[idx]
+
+            # Check if character is superscript
+            if new_char := superscript_map.get(char):
+                if not in_super:
+                    html_str += "<sup>"
+                    in_super = True
+                html_str += new_char
+            # Check if character is subscript
+            elif new_char := subscript_map.get(char):
+                if not in_sub:
+                    html_str += "<sub>"
+                    in_sub = True
+                html_str += new_char
+            else:
+                # Close any open tags
+                if in_super:
+                    html_str += "</sup>"
+                    in_super = False
+                if in_sub:
+                    html_str += "</sub>"
+                    in_sub = False
+                html_str += char
+            idx += 1
+
+        # Close any remaining open tags
+        if in_super:
+            html_str += "</sup>"
+        if in_sub:
+            html_str += "</sub>"
+
+        return html_str
 
     @property
     def category(self) -> str:
@@ -296,6 +366,7 @@ def __reduce_ex__(self, proto: object) -> tuple[type, tuple[str]]:
     cohesive_energy_per_atom = "cohesive_energy_per_atom"
     heat_of_formation = "heat_of_formation"
     heat_of_reaction = "heat_of_reaction"
+    e_form = "e_form"
     e_form_per_atom = "e_form_per_atom"
     e_form_pred = "e_form_pred"
     e_form_true = "e_form_true"
diff --git a/pymatviz/keys.yml b/pymatviz/keys.yml
index 58641b58..7e5c050e 100644
--- a/pymatviz/keys.yml
+++ b/pymatviz/keys.yml
@@ -151,7 +151,7 @@ electronic:
   mobility:
     label: Carrier Mobility
     symbol: μ
-    unit: cm²/V·s
+    unit: cm²/V⋅s
   effective_mass:
     label: Effective Mass
     symbol: m<sub>e</sub>
@@ -184,11 +184,11 @@ electronic:
   electron_mobility:
     label: Electron Mobility
     symbol: μ<sub>e</sub>
-    unit: cm²/V·s
+    unit: cm²/V⋅s
   hole_mobility:
     label: Hole Mobility
     symbol: μ<sub>h</sub>
-    unit: cm²/V·s
+    unit: cm²/V⋅s
 
 thermodynamic:
   energy:
@@ -248,6 +248,11 @@ thermodynamic:
     symbol: E<sub>coh</sub>/N<sub>atoms</sub>
     unit: eV/atom
     description: Energy required to break crystal into isolated neutral atoms
+  e_form:
+    label: E<sub>form</sub>
+    symbol: E<sub>form</sub>
+    unit: eV/atom
+    description: All-atoms formation energy relative to constituent element reference states
   e_form_per_atom:
     label: E<sub>form</sub>
     symbol: E<sub>form</sub>/N<sub>atoms</sub>
@@ -354,7 +359,7 @@ mechanical:
   fracture_toughness:
     label: Fracture Toughness
     symbol: K<sub>IC</sub>
-    unit: MPa·m<sup>1/2</sup>
+    unit: MPa⋅m½
   sound_velocity:
     label: Sound Velocity
     symbol: v<sub>s</sub>
@@ -362,7 +367,7 @@ mechanical:
   thermal_conductivity:
     label: Thermal Conductivity
     symbol: κ
-    unit: W/m·K
+    unit: W/m⋅K
   thermal_expansion:
     label: Thermal Expansion
     symbol: α
@@ -370,11 +375,11 @@ mechanical:
   lattice_thermal_conductivity:
     label: Lattice Thermal Conductivity
     symbol: κ<sub>lattice</sub>
-    unit: W/m·K
+    unit: W/m⋅K
   electronic_thermal_conductivity:
     label: Electronic Thermal Conductivity
     symbol: κ<sub>electronic</sub>
-    unit: W/m·K
+    unit: W/m⋅K
   heat_capacity:
     label: Heat Capacity
     symbol: C<sub>V</sub>
@@ -382,7 +387,7 @@ mechanical:
   specific_heat_capacity:
     label: Specific Heat Capacity
     symbol: c<sub>p</sub>
-    unit: J/kg·K
+    unit: J/kg⋅K
   thermal_expansion_coefficient:
     label: Thermal Expansion Coefficient
     symbol: α<sub>thermal</sub>
@@ -398,7 +403,7 @@ mechanical:
   viscosity:
     label: Viscosity
     symbol: η
-    unit: Pa·s
+    unit: Pa⋅s
   strain:
     label: Strain
     symbol: ε
@@ -456,7 +461,7 @@ thermal:
   thermal_resistivity:
     label: Thermal Resistivity
     symbol: ρ<sub>th</sub>
-    unit: K·m/W
+    unit: K⋅m/W
     description: Resistance to heat flow, inverse of thermal conductivity
   thermal_time_constant:
     label: Thermal Time Constant
@@ -473,7 +478,7 @@ magnetic:
   magnetic_moment:
     label: Magnetic Moment
     symbol: μ<sub>B</sub>
-    unit: μB
+    unit: μ<sub>B</sub>
   magmoms:
     label: Magnetic Moments
     symbol: μ
@@ -1134,6 +1139,7 @@ metrics:
   volume_error:
     label: Volume Error
     symbol: V<sub>err</sub>
+    unit: ų
   max_force_error:
     label: Max Force Error
   max_stress_error:
diff --git a/pymatviz/ptable/ptable_plotly.py b/pymatviz/ptable/ptable_plotly.py
index 6f2d154e..95944acb 100644
--- a/pymatviz/ptable/ptable_plotly.py
+++ b/pymatviz/ptable/ptable_plotly.py
@@ -312,7 +312,7 @@ def ptable_heatmap_plotly(
     if border is not False:
         border = border or {}
         border_color = border.pop("color", "darkgray")
-        border_width = border.pop("width", 2)
+        border_width = border.pop("width", 0.5)
 
         common_kwargs = dict(
             z=np.where(tile_texts, 1, np.nan), showscale=False, hoverinfo="none"
diff --git a/tests/ptable/plotly/test_ptable_plotly.py b/tests/ptable/plotly/test_ptable_plotly.py
index b207ffc1..737f6fdb 100644
--- a/tests/ptable/plotly/test_ptable_plotly.py
+++ b/tests/ptable/plotly/test_ptable_plotly.py
@@ -170,3 +170,44 @@ def custom_colorscale(_element_symbol: str, _value: float, split_idx: int) -> st
     for trace in fig.data:
         # Each element tile should have a color array with custom colors
         assert trace.fillcolor in {"rgb(255,0,0)", "rgb(0,0,255)"}
+
+
+def test_ptable_heatmap_plotly_colorbar() -> None:
+    """Test colorbar customization in ptable_heatmap_plotly."""
+    data = {"Fe": 1.234, "O": 5.678}
+
+    # Test colorbar title and formatting
+    colorbar = dict(
+        title="Test Title", tickformat=".2f", orientation="v", len=0.8, x=1.1
+    )
+
+    fig = pmv.ptable_heatmap_plotly(data, colorbar=colorbar)
+
+    # Get the colorbar from the figure
+    colorbar_trace = next(trace for trace in fig.data if hasattr(trace, "colorbar"))
+    actual_colorbar = colorbar_trace.colorbar
+
+    # Check colorbar properties were set correctly
+    assert actual_colorbar.title.text == "<br><br>Test Title"
+    assert actual_colorbar.tickformat == ".2f"
+    assert actual_colorbar.orientation == "v"
+    assert actual_colorbar.len == 0.8
+    assert actual_colorbar.x == 1.1
+
+    # Test horizontal colorbar title formatting
+    h_colorbar = dict(title="Horizontal Title", orientation="h", y=0.8)
+
+    fig = pmv.ptable_heatmap_plotly(data, colorbar=h_colorbar)
+    h_colorbar_trace = next(trace for trace in fig.data if hasattr(trace, "colorbar"))
+    actual_h_colorbar = h_colorbar_trace.colorbar
+
+    # Check horizontal colorbar properties
+    assert (
+        actual_h_colorbar.title.text == "Horizontal Title<br>"
+    )  # Horizontal title has break after
+    assert actual_h_colorbar.orientation == "h"
+    assert actual_h_colorbar.y == 0.8
+
+    # Test disabling colorbar
+    fig = pmv.ptable_heatmap_plotly(data, show_scale=False)
+    assert not any(trace.showscale for trace in fig.data)
diff --git a/tests/test_enums.py b/tests/test_enums.py
index bdfcee15..e052ca43 100644
--- a/tests/test_enums.py
+++ b/tests/test_enums.py
@@ -223,43 +223,42 @@ def test_key_units_are_consistent() -> None:
 
 
 def test_key_label_formatting() -> None:
-    """Test that labels are properly formatted."""
+    """Test that all labels are properly formatted."""
     for key in Key:
         label = key.label
-        assert (  # Label should be capitalized
+        assert (
             label[0].isupper() or label[0].isdigit() or label.startswith("r2SCAN")
-        ), f"Label should be capitalized: {label}"
+        ), f"{label=} should be capitalized"
 
-        assert not label.endswith((".", ",")), f"{label=} ends with period or comma"
+        assert not label.endswith((".", ",")), f"{label=} ends with punctuation"
 
         assert label.strip() == label, f"{label=} has outer whitespace"
 
-        assert "  " not in label, f"Label has multiple spaces: {label}"
+        assert "  " not in label, f"{label=} has multiple spaces"
 
 
 def test_key_value_matches_name() -> None:
-    """Test that Key enum values match their names."""
+    """Test that all Key enum values match their names."""
     for key in Key:
         # yield is a reserved word in Python, so had to be suffixed, hence can't match
         # key name can't match value
         if key in (Key.yield_, Key.mat_id):
             continue
-        assert str(key) == key.name.lower(), f"Value doesn't match name for {key}"
+        name, value = key.name, str(key)
+        assert name == value, f"{name=} doesn't match {value=}"
 
 
-def test_key_symbol_html_validity() -> None:
+def test_key_html_validity() -> None:
     """Test that HTML subscripts in symbols are properly formatted."""
     for key in Key:
-        symbol = key.symbol
-        if symbol and "<sub>" in symbol:
-            # Check matching closing tags
-            assert symbol.count("<sub>") == symbol.count(
-                "</sub>"
-            ), f"Mismatched sub tags in {symbol}"
-            # Check proper nesting
-            assert (
-                "</sub>" not in symbol[: symbol.index("<sub>")]
-            ), f"Improper tag nesting in {symbol}"
+        for field in ("symbol", "unit"):
+            value = getattr(key, field)
+            if value and "<sub>" in value:
+                # Check matching closing tags
+                n_sub, n_sub_end = value.count("<sub>"), value.count("</sub>")
+                assert n_sub == n_sub_end, f"Mismatched sub tags in {value}"
+                # Check proper nesting
+                assert "</sub>" not in value[: value.index("<sub>")]
 
 
 @pytest.mark.parametrize(
@@ -279,10 +278,104 @@ def test_key_descriptions(key: Key, expected_description: str | None) -> None:
     assert key.desc == expected_description, f"Unexpected description for {key}"
 
 
-def test_key_description_field_name() -> None:
-    """Test that the description field in YAML is accessed correctly."""
-    from pymatviz.enums import _keys
+@pytest.mark.parametrize(
+    ("key", "expected_unit"),
+    [
+        # Basic units
+        (Key.volume, "Å<sup>3</sup>"),
+        (Key.energy, "eV"),
+        (Key.temperature, "K"),
+        (Key.pressure, "Pa"),
+        # Complex units
+        (Key.carrier_concentration, "cm<sup>-3</sup>"),
+        (Key.mobility, "cm<sup>2</sup>/V⋅s"),
+        (Key.thermal_conductivity, "W/m⋅K"),
+        (Key.fracture_toughness, "MPa⋅m<sup>1/2</sup>"),
+        # Units with subscripts
+        (Key.magnetic_moment, "μ<sub>B</sub>"),
+        (Key.energy_per_atom, "eV/atom"),
+        (Key.heat_capacity, "J/K"),
+        # Mixed sub/superscripts
+        (Key.specific_heat_capacity, "J/kg⋅K"),
+        (Key.thermal_resistivity, "K⋅m/W"),
+        # No units
+        (Key.formula, None),
+        (Key.structure, None),
+        (Key.crystal_system, None),
+    ],
+)
+def test_key_units(key: Key, expected_unit: str | None) -> None:
+    """Test that Key enum units are correctly formatted with HTML tags."""
+    assert key.unit == expected_unit
+
+
+def test_unit_html_consistency() -> None:
+    """Test that all units follow consistent HTML formatting rules."""
+    for key in Key:
+        unit = key.unit
+        if unit is None:
+            continue
 
-    # Check that descriptions use "description" not "desc" in YAML data
-    keys_with_desc = [k for k, v in _keys.items() if "description" in v]
-    assert len(keys_with_desc) >= 50, "No descriptions found in YAML data"
+        # Check proper HTML tag nesting
+        if "<sup>" in unit:
+            assert unit.count("<sup>") == unit.count(
+                "</sup>"
+            ), f"Mismatched sup tags in {unit}"
+            assert (
+                "</sup>" not in unit[: unit.index("<sup>")]
+            ), f"Improper sup tag nesting in {unit}"
+
+        if "<sub>" in unit:
+            assert unit.count("<sub>") == unit.count(
+                "</sub>"
+            ), f"Mismatched sub tags in {unit}"
+            assert (
+                "</sub>" not in unit[: unit.index("<sub>")]
+            ), f"Improper sub tag nesting in {unit}"
+
+        # Check no nested tags
+        if "<sup>" in unit and "<sub>" in unit:
+            sup_start = unit.index("<sup>")
+            sup_end = unit.index("</sup>")
+            sub_start = unit.index("<sub>")
+            sub_end = unit.index("</sub>")
+            assert not (sup_start < sub_start < sup_end), "Nested sup/sub tags"
+            assert not (sub_start < sup_start < sub_end), "Nested sub/sup tags"
+
+
+def test_unit_special_characters() -> None:
+    """Test that special characters in units are consistently used."""
+    for key in Key:
+        unit = key.unit
+        if unit is None:
+            continue
+
+        # Check for proper middle dot usage
+        assert "·" not in unit, f"ASCII middle dot in {unit}, use ⋅ instead"
+
+        # Check for proper minus sign usage
+        if "-" in unit:
+            assert (
+                "<sup>-" in unit
+            ), f"ASCII hyphen in {unit}, use <sup>-...</sup> for exponents"
+
+        # Common units should use standard symbols
+        if "angstrom" in unit:
+            assert "Å" in unit, f"Use Å symbol in {unit} of {key}"
+        if "micro" in unit:
+            assert "μ" in unit, f"Use μ symbol in {unit} of {key}"
+        if "ohm" in unit:
+            assert "Ω" in unit, f"Use Ω symbol in {unit} of {key}"
+        if "kelvin" in unit:
+            assert "K" in unit, f"Use K symbol in {unit} of {key}"
+        if "pascal" in unit:
+            assert "Pa" in unit, f"Use Pa symbol in {unit} of {key}"
+
+
+def test_unit_formatting_consistency() -> None:
+    """Test that similar quantities use consistent unit formatting."""
+    ev_keys = {k for k in Key if k.unit and "eV" in k.unit}
+    valid_ev_units = {"eV", "eV/atom", "eV/K", "eV/Å", "meV"}
+    for key in ev_keys:
+        unit = key.unit
+        assert unit in valid_ev_units, f"Unexpected {unit=} for {key=}"