diff --git a/.gitignore b/.gitignore
index d3acf13..b4a8eaf 100644
--- a/.gitignore
+++ b/.gitignore
@@ -49,6 +49,7 @@ coverage.xml
 *.cover
 .hypothesis/
 .pytest_cache/
+prof/
 
 # Translations
 *.mo
diff --git a/gemd/__version__.py b/gemd/__version__.py
index 8a124bf..b19ee4b 100644
--- a/gemd/__version__.py
+++ b/gemd/__version__.py
@@ -1 +1 @@
-__version__ = "2.2.0"
+__version__ = "2.2.1"
diff --git a/gemd/demo/cake.py b/gemd/demo/cake.py
index 8586dac..794744f 100644
--- a/gemd/demo/cake.py
+++ b/gemd/demo/cake.py
@@ -1,5 +1,5 @@
 """Bake a cake."""
-from importlib_resources import files
+from importlib.resources import files
 from io import BytesIO
 import random
 
diff --git a/gemd/demo/strehlow_and_cook.py b/gemd/demo/strehlow_and_cook.py
index 11e1035..fe8f662 100644
--- a/gemd/demo/strehlow_and_cook.py
+++ b/gemd/demo/strehlow_and_cook.py
@@ -45,7 +45,7 @@
 
 def import_table(filename=SMALL_TABLE):
     """Return the deserialized JSON table."""
-    from importlib_resources import files
+    from importlib.resources import files
     import json
 
     return json.loads(files("gemd.demo").joinpath(filename).read_text(encoding='utf-8'))
diff --git a/gemd/units/impl.py b/gemd/units/impl.py
index dfdccf7..0815d9c 100644
--- a/gemd/units/impl.py
+++ b/gemd/units/impl.py
@@ -1,23 +1,25 @@
 """Implementation of units."""
 from deprecation import deprecated
 import functools
-from importlib_resources import files
+from importlib.resources import files
 import os
 from pathlib import Path
 import re
 from tempfile import TemporaryDirectory
 from typing import Union, List, Tuple, Generator, Any
+try:
+    from typing import TypeAlias  # Python 3.10+
+except ImportError:  # pragma nocover
+    from typing_extensions import TypeAlias  # Python 3.9
 
 from pint import UnitRegistry, register_unit_format
-try:  # Pint 0.23 migrated the location of this method, and augmented it
-    from pint.pint_eval import tokenizer
-except ImportError:  # pragma: no cover
-    from pint.compat import tokenizer
+from pint.pint_eval import tokenizer
 from tokenize import NAME, NUMBER, OP, ERRORTOKEN, TokenInfo
 # alias the error that is thrown when units are incompatible
 # this helps to isolate the dependence on pint
-from pint.errors import DimensionalityError as IncompatibleUnitsError  # noqa Import
-from pint.errors import UndefinedUnitError, DefinitionSyntaxError  # noqa Import
+from pint.errors import DimensionalityError as IncompatibleUnitsError
+from pint.errors import UndefinedUnitError, DefinitionSyntaxError
+from pint.registry import GenericUnitRegistry
 
 # Store directories so they don't get auto-cleaned until exit
 _TEMP_DIRECTORY = TemporaryDirectory()
@@ -216,43 +218,29 @@ def _unmangle_scaling(input_string: str) -> str:
     return input_string
 
 
-try:  # pragma: no cover
-    # Pint 0.23 modified the preferred way to derive a custom class
-    # https://pint.readthedocs.io/en/0.23/advanced/custom-registry-class.html
-    from pint.registry import GenericUnitRegistry
-    from typing_extensions import TypeAlias
+# Standard approach to creating a custom registry class:
+# https://pint.readthedocs.io/en/0.23/advanced/custom-registry-class.html
 
-    class _ScaleFactorUnit(UnitRegistry.Unit):
-        """Child class of Units for generating units w/ clean scaling factors."""
+class _ScaleFactorUnit(UnitRegistry.Unit):
+    """Child class of Units for generating units w/ clean scaling factors."""
 
-        def __format__(self, format_spec):
-            result = super().__format__(format_spec)
-            return _unmangle_scaling(result)
+    def __format__(self, format_spec):
+        result = super().__format__(format_spec)
+        return _unmangle_scaling(result)
 
-    class _ScaleFactorQuantity(UnitRegistry.Quantity):
-        """Child class of Quantity for generating units w/ clean scaling factors."""
 
-        pass
-
-    class _ScaleFactorRegistry(GenericUnitRegistry[_ScaleFactorQuantity, _ScaleFactorUnit]):
-        """UnitRegistry class that uses _GemdUnits."""
+class _ScaleFactorQuantity(UnitRegistry.Quantity):
+    """Child class of Quantity for generating units w/ clean scaling factors."""
 
-        Quantity: TypeAlias = _ScaleFactorQuantity
-        Unit: TypeAlias = _ScaleFactorUnit
+    pass
 
-except ImportError:  # pragma: no cover
-    # https://pint.readthedocs.io/en/0.21/advanced/custom-registry-class.html
-    class _ScaleFactorUnit(UnitRegistry.Unit):
-        """Child class of Units for generating units w/ clean scaling factors."""
 
-        def __format__(self, format_spec):
-            result = super().__format__(format_spec)
-            return _unmangle_scaling(result)
+class _ScaleFactorRegistry(GenericUnitRegistry[_ScaleFactorQuantity, _ScaleFactorUnit]):
+    """UnitRegistry class that uses _GemdUnits."""
 
-    class _ScaleFactorRegistry(UnitRegistry):
-        """UnitRegistry class that uses _GemdUnits."""
+    Quantity: TypeAlias = _ScaleFactorQuantity
+    Unit: TypeAlias = _ScaleFactorUnit
 
-        _unit_class = _ScaleFactorUnit
 
 _REGISTRY: _ScaleFactorRegistry = None  # global requires it be defined in this scope
 
diff --git a/pyproject.toml b/pyproject.toml
new file mode 100644
index 0000000..bea72a3
--- /dev/null
+++ b/pyproject.toml
@@ -0,0 +1,73 @@
+[project]
+name = "gemd"
+dynamic = ["version"]
+dependencies = [
+    "pint>=0.24.4,<0.25",
+    "deprecation>=2.1.0,<3",
+    "typing_extensions>=4.8,<5; python_version<'3.10'",
+]
+requires-python = ">=3.9"
+authors = [
+    {name = "Citrine Informatics"}
+]
+description = "Python binding for Citrine's GEMD data model"
+readme = "README.md"
+license-files = ["LICENSE"]
+classifiers = [
+          "Programming Language :: Python :: 3",
+          "Programming Language :: Python :: 3.9",
+          "Programming Language :: Python :: 3.10",
+          "Programming Language :: Python :: 3.11",
+          "Programming Language :: Python :: 3.12",
+          "Programming Language :: Python :: 3.13",
+]
+
+[project.urls]
+Homepage = "http://github.com/CitrineInformatics/gemd-python"
+
+[build-system]
+requires = ["setuptools>=61.0", "wheel"]
+build-backend = "setuptools.build_meta"
+
+[tool.setuptools.dynamic]
+version = {attr = "gemd.__version__.__version__"}
+
+[tool.setuptools.packages.find]
+where = ["."]
+include = ["gemd"]
+exclude = ["docs", "tests"]
+
+[tool.setuptools.package-data]
+"gemd.demo" = ["strehlow_and_cook.pif", "strehlow_and_cook_small.pif", "toothpick.jpg"]
+"gemd.units" = ["citrine_en.txt", "constants_en.txt"]
+"tests.units" = ["test_units.txt"]
+
+
+[dependency-groups]
+dev = [
+    "flake8==7.0.0",
+    "flake8-docstrings==1.7.0",
+    "numpy==1.24.4; python_version<'3.10'",
+    "pandas==2.0.3; python_version<'3.10'",
+    "numpy>=2.0.2,<=2.1.0; python_version>='3.10'",
+    "pandas==2.3.0; python_version>='3.10'",
+    "pytest==8.4.2",
+    "pytest-cov==7.0.0",
+    "derp==0.1.1",
+    "tomli>=2.2.1",
+]
+docs = [
+    "sphinx==5.0.0",
+    "sphinx-rtd-theme==1.0.0",
+    "sphinxcontrib-apidoc==0.3.0",
+]
+
+[tool.pytest.ini_options]
+testpaths = [
+    "tests",
+]
+
+[tool.coverage.run]
+omit = [
+    "gemd/demo/*",
+]
diff --git a/requirements.txt b/requirements.txt
index bc1d0b6..0af944d 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,4 +1,3 @@
 pint==0.24.4
 deprecation==2.1.0
-typing-extensions==4.8.0
-importlib-resources==5.3.0
+typing_extensions>=4.8,<5; python_version<'3.10'
diff --git a/scripts/run_tests.sh b/scripts/run_tests.sh
index a44c40b..b24d9ee 100755
--- a/scripts/run_tests.sh
+++ b/scripts/run_tests.sh
@@ -36,8 +36,9 @@ then python $REPO_DIR/scripts/validate_version_bump.py                        ||
 fi
 
 flake8 $REPO_DIR/gemd                                                         || exit 1;
-derp $REPO_DIR $REPO_DIR/gemd/__version__.py                                  || exit 1;
+derp $REPO_DIR/gemd $REPO_DIR/gemd/__version__.py                             || exit 1;
 pytest $QUIET $EXITFIRST --cov=$REPO_DIR/gemd                                \
        --cov-report term-missing:skip-covered                                \
-       --cov-config=$REPO_DIR/tox.ini --no-cov-on-fail --cov-fail-under=100  \
+       --cov-config=$REPO_DIR/pyproject.toml                                 \
+       --no-cov-on-fail --cov-fail-under=100                                 \
        $REPO_DIR                                                              || exit 1;
diff --git a/setup.py b/setup.py
deleted file mode 100644
index cb33c7d..0000000
--- a/setup.py
+++ /dev/null
@@ -1,67 +0,0 @@
-from setuptools import setup, find_packages
-from pathlib import Path
-import re
-
-packages = find_packages()
-
-this_directory = Path(__file__).parent.absolute()
-version_file = this_directory / 'gemd' / '__version__.py'
-version_re = r'''^\s*__version__\s*=\s*(['"])([\w\.]+)\1$'''
-if mo := re.search(version_re, version_file.read_text(), re.M):
-    version = mo.group(2)
-else:
-    raise RuntimeError(f"Unable to find version string in {version_file}")
-
-setup(name='gemd',
-      # Update this in gemd/__version__.py
-      version=version,
-      python_requires='>=3.9',
-      url='http://github.com/CitrineInformatics/gemd-python',
-      description="Python binding for Citrine's GEMD data model",
-      author='Citrine Informatics',
-      packages=packages,
-      package_data={
-          'gemd.demo': [
-              'strehlow_and_cook.pif',
-              'strehlow_and_cook_small.pif',
-              'toothpick.jpg'
-          ],
-          'gemd.units': [
-              'citrine_en.txt',
-              'constants_en.txt',
-          ],
-          'tests.units': ['test_units.txt']
-      },
-      install_requires=[
-          "pint>=0.24.4,<0.25",
-          "deprecation>=2.1.0,<3",
-          "typing_extensions>=4.8,<5",
-          "importlib-resources>=5.3,<7"
-      ],
-      extras_require={
-          "scripts": [
-              "packaging",
-              "sphinx==5.0.0",
-              "sphinx-rtd-theme==1.0.0",
-              "sphinxcontrib-apidoc==0.3.0",
-          ],
-          "tests": [
-              "pytest>=8.0.0,<9"
-          ],
-          "tests.demo": [
-              "pandas>=2.0.3,<3"
-          ],
-          "tests.entity.bounds": [
-              "numpy>=1.24.4,<2; python_version<='3.10'",
-              "pandas>=2.0.3,<3"
-          ]
-      },
-      classifiers=[
-          'Programming Language :: Python :: 3',
-          'Programming Language :: Python :: 3.9',
-          'Programming Language :: Python :: 3.10',
-          'Programming Language :: Python :: 3.11',
-          'Programming Language :: Python :: 3.12',
-          'Programming Language :: Python :: 3.13',
-      ],
-      )
diff --git a/test_requirements.txt b/test_requirements.txt
index 0460dfc..c8f0654 100644
--- a/test_requirements.txt
+++ b/test_requirements.txt
@@ -4,6 +4,6 @@ numpy==1.24.4; python_version<'3.10'
 pandas==2.0.3; python_version<'3.10'
 numpy>=2.0.2,<=2.1.0; python_version>='3.10'
 pandas==2.3.0; python_version>='3.10'
-pytest==8.0.0
-pytest-cov==4.1.0
+pytest==8.4.2
+pytest-cov==7.0.0
 derp==0.1.1
diff --git a/tests/units/test_parser.py b/tests/units/test_parser.py
index 3706399..ffcdeac 100644
--- a/tests/units/test_parser.py
+++ b/tests/units/test_parser.py
@@ -1,6 +1,6 @@
 from contextlib import contextmanager
 from deprecation import DeprecatedWarning
-from importlib_resources import files
+from importlib.resources import files
 import re
 from pint import UnitRegistry
 import pytest
diff --git a/tox.ini b/tox.ini
index 1cd27cc..881efa9 100644
--- a/tox.ini
+++ b/tox.ini
@@ -11,8 +11,5 @@ max-doc-length = 119
 # D401: Imperative mood requirement basically gets in the way
 ignore = D100,D104,D105,D107,D301,D401
 
-[pytest]
-testpaths = tests
-
 [run]
-omit = gemd/demo/*
+omit = gemd/demo/*
\ No newline at end of file