diff --git "a/react-frontend/src/components/ProfileCard.js\n```javascript\nimport React from 'react';\nimport PropTypes from 'prop-types';\nimport './ProfileCard.css'; / Assuming there is a CSS file for styling\n\nconst ProfileCard = ({ user }) =_ {\n  return (\n    _div className=_profile-card__\n      _img src={user.profileImage} alt={`${user.name}'s profile`} className=_profile-image_ /_\n      _h2 className=_profile-name__{user.name}_/h2_\n      _p className=_profile-email__{user.email}_/p_\n      _p className=_profile-bio__{user.bio}_/p_ {/_ New bio information added _/}\n      _a href={`mailto_${user.email}`} className=_contact-link__Contact_/a_\n    _/div_\n  );\n};\n\nProfileCard.propTypes = {\n  user_ PropTypes.shape({\n    name_ PropTypes.string.isRequired,\n    profileImage_ PropTypes.string.isRequired,\n    email_ PropTypes.string.isRequired,\n    bio_ PropTypes.string, / New bio prop\n  }).isRequired,\n};\n\nexport default ProfileCard;" "b/react-frontend/src/components/ProfileCard.js\n```javascript\nimport React from 'react';\nimport PropTypes from 'prop-types';\nimport './ProfileCard.css'; / Assuming there is a CSS file for styling\n\nconst ProfileCard = ({ user }) =_ {\n  return (\n    _div className=_profile-card__\n      _img src={user.profileImage} alt={`${user.name}'s profile`} className=_profile-image_ /_\n      _h2 className=_profile-name__{user.name}_/h2_\n      _p className=_profile-email__{user.email}_/p_\n      _p className=_profile-bio__{user.bio}_/p_ {/_ New bio information added _/}\n      _a href={`mailto_${user.email}`} className=_contact-link__Contact_/a_\n    _/div_\n  );\n};\n\nProfileCard.propTypes = {\n  user_ PropTypes.shape({\n    name_ PropTypes.string.isRequired,\n    profileImage_ PropTypes.string.isRequired,\n    email_ PropTypes.string.isRequired,\n    bio_ PropTypes.string, / New bio prop\n  }).isRequired,\n};\n\nexport default ProfileCard;"
new file mode 100644
index 000000000..55b0e207e
--- /dev/null
+++ "b/react-frontend/src/components/ProfileCard.js\n```javascript\nimport React from 'react';\nimport PropTypes from 'prop-types';\nimport './ProfileCard.css'; / Assuming there is a CSS file for styling\n\nconst ProfileCard = ({ user }) =_ {\n  return (\n    _div className=_profile-card__\n      _img src={user.profileImage} alt={`${user.name}'s profile`} className=_profile-image_ /_\n      _h2 className=_profile-name__{user.name}_/h2_\n      _p className=_profile-email__{user.email}_/p_\n      _p className=_profile-bio__{user.bio}_/p_ {/_ New bio information added _/}\n      _a href={`mailto_${user.email}`} className=_contact-link__Contact_/a_\n    _/div_\n  );\n};\n\nProfileCard.propTypes = {\n  user_ PropTypes.shape({\n    name_ PropTypes.string.isRequired,\n    profileImage_ PropTypes.string.isRequired,\n    email_ PropTypes.string.isRequired,\n    bio_ PropTypes.string, / New bio prop\n  }).isRequired,\n};\n\nexport default ProfileCard;"	
@@ -0,0 +1,5 @@
+### Back-end: Spring Boot Controller Modification
+
+Let's assume we need to modify a controller to handle a new endpoint or adjust existing logic.
+
+FILE_OPERATION: MODIFY spring-backend/src/main/java/com/example/application/controller/UserController.java
\ No newline at end of file
diff --git a/spring-backend/src/main/java/com/example/application/service/UserService.java b/spring-backend/src/main/java/com/example/application/service/UserService.java
new file mode 100644
index 000000000..1da0e5a56
--- /dev/null
+++ b/spring-backend/src/main/java/com/example/application/service/UserService.java
@@ -0,0 +1,33 @@
+java
+package com.example.application.service;
+
+import com.example.application.model.User;
+import com.example.application.repository.UserRepository;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Service;
+
+import java.util.List;
+
+@Service
+public class UserService {
+
+    @Autowired
+    private UserRepository userRepository;
+
+    public List<User> findAllUsers() {
+        return userRepository.findAll();
+    }
+
+    public User findUserById(Long id) {
+        return userRepository.findById(id).orElse(null);
+    }
+
+    public User updateUserBio(Long id, String bio) {
+        User user = userRepository.findById(id).orElse(null);
+        if (user != null) {
+            user.setBio(bio);
+            userRepository.save(user);
+        }
+        return user;
+    }
+}
\ No newline at end of file