diff --git a/src/healthsciencecalculator/healthsciencecalculator.py b/src/healthsciencecalculator/healthsciencecalculator.py
index e69de29..1c9ee1a 100644
--- a/src/healthsciencecalculator/healthsciencecalculator.py
+++ b/src/healthsciencecalculator/healthsciencecalculator.py
@@ -0,0 +1,40 @@
+from dataclasses import dataclass
+
+
+@dataclass
+class BMIResult:
+    bmi: float
+    category: str
+    risk_level: str
+
+
+def get_bmi(
+    weight: float,
+    height: float,
+) -> BMIResult:
+    """Calculate Body Mass Index (BMI) and return detailed classification information.
+
+    BMI is calculated as weight (kg) divided by height (m) squared.
+
+    Parameters
+    ----------
+    weight : float
+        Weight in kilograms
+    height : float
+        Height in meters
+
+    Returns
+    -------
+    BMIResult
+        A dataclass containing:
+        - bmi (float): The calculated BMI value
+        - category (str): BMI category, one of:
+            - 'underweight' (BMI < 18.5)
+            - 'healthy' (BMI 18.5-24.9)
+            - 'overweight' (BMI 25-29.9)
+            - 'class 1 obesity' (BMI 30-34.9)
+            - 'class 2 obesity' (BMI 35-39.9)
+            - 'class 3 obesity' (BMI >= 40)
+        - risk_level (str): Associated health risk level
+    """
+    return