diff --git a/app/src/main/java/org/mercury_im/messenger/ui/roster/contacts/detail/ContactDetailFragment.java b/app/src/main/java/org/mercury_im/messenger/ui/roster/contacts/detail/ContactDetailFragment.java
index cc5d215..91bc0de 100644
--- a/app/src/main/java/org/mercury_im/messenger/ui/roster/contacts/detail/ContactDetailFragment.java
+++ b/app/src/main/java/org/mercury_im/messenger/ui/roster/contacts/detail/ContactDetailFragment.java
@@ -8,6 +8,7 @@ import android.util.Log;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
+import android.widget.Button;
 import android.widget.EditText;
 import android.widget.ImageView;
 import android.widget.TextView;
@@ -18,6 +19,7 @@ import androidx.fragment.app.Fragment;
 import androidx.lifecycle.ViewModelProvider;
 import androidx.lifecycle.ViewModelStoreOwner;
 
+import com.google.android.material.chip.Chip;
 import com.google.android.material.chip.ChipGroup;
 import com.google.android.material.floatingactionbutton.ExtendedFloatingActionButton;
 
@@ -26,10 +28,11 @@ import org.mercury_im.messenger.R;
 import org.mercury_im.messenger.ui.chat.ChatActivity;
 import org.mercury_im.messenger.util.ColorUtil;
 
+import java.util.List;
+
 import butterknife.BindView;
 import butterknife.ButterKnife;
 import io.reactivex.Completable;
-import io.reactivex.Observable;
 import io.reactivex.android.schedulers.AndroidSchedulers;
 import io.reactivex.schedulers.Schedulers;
 
@@ -59,6 +62,9 @@ public class ContactDetailFragment extends Fragment {
     @BindView(R.id.fab)
     ExtendedFloatingActionButton fab;
 
+    @BindView(R.id.button_add_to_group)
+    Button button;
+
     private ContactDetailViewModel viewModel;
 
     @Nullable
@@ -98,6 +104,15 @@ public class ContactDetailFragment extends Fragment {
             }
         });
 
+        button.setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View v) {
+                viewModel.addContactToRosterGroup().subscribeOn(Schedulers.io())
+                        .observeOn(AndroidSchedulers.mainThread())
+                        .subscribe();
+            }
+        });
+
         return view;
     }
 
@@ -132,5 +147,24 @@ public class ContactDetailFragment extends Fragment {
         viewModel.getContactAddress().observe(this, address -> contactAddress.setText(address));
         viewModel.getContactPresenceStatus().observe(this, presenceText -> contactPresence.setText(presenceText));
         viewModel.getContactAccountAddress().observe(this, address -> contactAccount.setText(address));
+        viewModel.getContactGroups().observe(this, this::setRosterGroups);
+    }
+
+    private void setRosterGroups(List<String> groups) {
+        contactGroups.removeAllViews();
+        for (String group : groups) {
+            Chip chip = new Chip(contactGroups.getContext());
+            chip.setText(group);
+            chip.setOnLongClickListener(new View.OnLongClickListener() {
+                @Override
+                public boolean onLongClick(View v) {
+                    viewModel.removeContactFromRosterGroup(group)
+                    .subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread())
+                    .subscribe();
+                    return true;
+                }
+            });
+            contactGroups.addView(chip);
+        }
     }
 }
diff --git a/app/src/main/java/org/mercury_im/messenger/ui/roster/contacts/detail/ContactDetailViewModel.java b/app/src/main/java/org/mercury_im/messenger/ui/roster/contacts/detail/ContactDetailViewModel.java
index fe0c2be..db4524e 100644
--- a/app/src/main/java/org/mercury_im/messenger/ui/roster/contacts/detail/ContactDetailViewModel.java
+++ b/app/src/main/java/org/mercury_im/messenger/ui/roster/contacts/detail/ContactDetailViewModel.java
@@ -14,6 +14,8 @@ import org.jivesoftware.smack.packet.Presence;
 import org.jivesoftware.smack.roster.PresenceEventListener;
 import org.jivesoftware.smack.roster.Roster;
 import org.jivesoftware.smack.roster.RosterEntry;
+import org.jivesoftware.smack.roster.RosterGroup;
+import org.jxmpp.jid.BareJid;
 import org.jxmpp.jid.Jid;
 import org.jxmpp.jid.impl.JidCreate;
 import org.mercury_im.messenger.MercuryImApplication;
@@ -23,10 +25,15 @@ import org.mercury_im.messenger.entity.contact.Peer;
 import org.mercury_im.messenger.ui.avatar.AvatarDrawable;
 import org.mercury_im.messenger.util.CombinedPresenceListener;
 
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
 import java.util.UUID;
+import java.util.stream.Collectors;
 
 import javax.inject.Inject;
 
+import io.reactivex.Completable;
 import io.reactivex.android.schedulers.AndroidSchedulers;
 import io.reactivex.disposables.CompositeDisposable;
 import io.reactivex.schedulers.Schedulers;
@@ -46,6 +53,7 @@ public class ContactDetailViewModel extends ViewModel {
     private MutableLiveData<String> contactPresenceStatus = new MutableLiveData<>("Going down the rabbit hole.");
     private MutableLiveData<String> contactName = new MutableLiveData<>("Alice Wonderland");
     private MutableLiveData<String> contactAccountAddress = new MutableLiveData<>("mad@hatter.lit");
+    private MutableLiveData<List<String>> contactGroups = new MutableLiveData<>(Collections.emptyList());
 
     private Roster roster;
 
@@ -58,6 +66,8 @@ public class ContactDetailViewModel extends ViewModel {
 
     public void bind(UUID accountId, String peerAddress) {
         Log.d("MMMMMM", "Bind!");
+        roster = Roster.getInstanceFor(messenger.getConnectionManager().getConnection(accountId).getConnection());
+        roster.addPresenceEventListener(presenceEventListener);
         contactAddress.setValue(peerAddress);
         contactAccountId.setValue(accountId);
         disposable.add(peerRepository.observePeerByAddress(accountId, peerAddress)
@@ -71,12 +81,21 @@ public class ContactDetailViewModel extends ViewModel {
                     contactAccountAddress.setValue(peer.getAccount().getAddress());
                     contactAvatar.setValue(new AvatarDrawable(peer.getDisplayName(), peer.getAddress()));
                     contactName.setValue(peer.getDisplayName());
+
+                    RosterEntry entry = roster.getEntry(JidCreate.entityBareFromOrThrowUnchecked(peerAddress));
+                    if (entry != null) {
+                        List<RosterGroup> groups = entry.getGroups();
+                        List<String> groupNames = new ArrayList<>(groups.size());
+                        for (RosterGroup g : groups) {
+                            groupNames.add(g.getName());
+                        }
+                        contactGroups.postValue(groupNames);
+                    }
                 }));
 
-        roster = Roster.getInstanceFor(messenger.getConnectionManager().getConnection(accountId).getConnection());
-        roster.addPresenceEventListener(presenceEventListener);
+        BareJid jid = JidCreate.entityBareFromOrThrowUnchecked(peerAddress);
 
-        Presence presence = roster.getPresence(JidCreate.entityBareFromOrThrowUnchecked(peerAddress));
+        Presence presence = roster.getPresence(jid);
         if (presence != null) {
             contactPresenceMode.postValue(presence.getMode());
             contactPresenceStatus.postValue(presence.getStatus());
@@ -120,6 +139,10 @@ public class ContactDetailViewModel extends ViewModel {
         return contactAccountAddress;
     }
 
+    public LiveData<List<String>> getContactGroups() {
+        return contactGroups;
+    }
+
     private final PresenceEventListener presenceEventListener = new CombinedPresenceListener() {
         @Override
         public void presenceReceived(Jid address, Presence presence) {
@@ -138,4 +161,28 @@ public class ContactDetailViewModel extends ViewModel {
                     entry.setName(newName);
         }
     }
+
+    public Completable addContactToRosterGroup() {
+        return Completable.fromAction(() -> doAddContactToRosterGroup());
+    }
+
+    private void doAddContactToRosterGroup() throws XMPPException.XMPPErrorException, SmackException.NotConnectedException, InterruptedException, SmackException.NoResponseException {
+        String groupName = "Mercury Seven";
+        RosterGroup group = roster.getGroup(groupName);
+        if (group == null) {
+            group = roster.createGroup(groupName);
+        }
+        BareJid jid = JidCreate.entityBareFromOrThrowUnchecked(getContactAddress().getValue());
+        if (group.contains(jid)) {
+            return;
+        }
+
+        RosterEntry entry = roster.getEntry(jid);
+        group.addEntry(entry);
+    }
+
+    public Completable removeContactFromRosterGroup(String group) {
+        return Completable.fromAction(() -> roster.getGroup(group).removeEntry(roster.getEntry(JidCreate.entityBareFromOrThrowUnchecked(getContactAddress().getValue()))));
+
+    }
 }
diff --git a/app/src/main/res/layout/fragment_contact_details.xml b/app/src/main/res/layout/fragment_contact_details.xml
index c59483c..f4110fd 100644
--- a/app/src/main/res/layout/fragment_contact_details.xml
+++ b/app/src/main/res/layout/fragment_contact_details.xml
@@ -143,6 +143,12 @@
                         android:text="Dungeons n' Dragons"/>
 
                 </com.google.android.material.chip.ChipGroup>
+
+                <Button
+                    android:id="@+id/button_add_to_group"
+                    android:layout_width="wrap_content"
+                    android:layout_height="wrap_content"
+                    android:text="Mark Mercury Seven"/>
             </LinearLayout>
 
         </androidx.cardview.widget.CardView>
diff --git a/data/src/main/java/org/mercury_im/messenger/data/model/AbstractPeerModel.java b/data/src/main/java/org/mercury_im/messenger/data/model/AbstractPeerModel.java
index 5a4e13e..cf151de 100644
--- a/data/src/main/java/org/mercury_im/messenger/data/model/AbstractPeerModel.java
+++ b/data/src/main/java/org/mercury_im/messenger/data/model/AbstractPeerModel.java
@@ -3,6 +3,7 @@ package org.mercury_im.messenger.data.model;
 import org.mercury_im.messenger.data.converter.SubscriptionDirectionConverter;
 import org.mercury_im.messenger.entity.contact.SubscriptionDirection;
 
+import java.util.List;
 import java.util.UUID;
 
 import io.requery.CascadeAction;
@@ -42,6 +43,9 @@ public abstract class AbstractPeerModel implements Persistable {
     @Convert(SubscriptionDirectionConverter.class)
     SubscriptionDirection subscriptionDirection;
 
+    @Column
+    List<String> groupNames;
+
     boolean subscriptionPending;
 
     boolean subscriptionPreApproved;
diff --git a/domain/src/main/java/org/mercury_im/messenger/store/MercuryRosterStore.java b/domain/src/main/java/org/mercury_im/messenger/store/MercuryRosterStore.java
index e53fc1e..fb1025c 100644
--- a/domain/src/main/java/org/mercury_im/messenger/store/MercuryRosterStore.java
+++ b/domain/src/main/java/org/mercury_im/messenger/store/MercuryRosterStore.java
@@ -198,6 +198,9 @@ public class MercuryRosterStore implements RosterStore {
         }
         item.setApproved(contactModel.isSubscriptionApproved());
         item.setSubscriptionPending(contactModel.isSubscriptionPending());
+        for (String groupName : contactModel.getGroupNames()) {
+            item.addGroupName(groupName);
+        }
         return item;
     }
 
@@ -210,7 +213,7 @@ public class MercuryRosterStore implements RosterStore {
         }
         peer.setSubscriptionApproved(item.isApproved());
         peer.setSubscriptionPending(item.isSubscriptionPending());
-
+        peer.setGroupNames(new ArrayList<>(item.getGroupNames()));
         return peer;
     }
 
diff --git a/domain/src/main/java/org/mercury_im/messenger/xmpp/CsiManager.java b/domain/src/main/java/org/mercury_im/messenger/xmpp/CsiManager.java
index f380595..183d08c 100644
--- a/domain/src/main/java/org/mercury_im/messenger/xmpp/CsiManager.java
+++ b/domain/src/main/java/org/mercury_im/messenger/xmpp/CsiManager.java
@@ -36,7 +36,7 @@ public class CsiManager implements ClientStateListener {
     private void tryCsiActive(MercuryConnection connection) {
         try {
             ClientStateIndicationManager.active(connection.getConnection());
-        } catch (SmackException.NotConnectedException | InterruptedException e) {
+        } catch (SmackException.NotConnectedException | InterruptedException | IllegalArgumentException e) {
             LOGGER.log(Level.WARNING, "Sending CSI state 'active' failed.", e);
         }
     }
@@ -44,7 +44,7 @@ public class CsiManager implements ClientStateListener {
     private void tryCsiInactive(MercuryConnection connection) {
         try {
             ClientStateIndicationManager.inactive(connection.getConnection());
-        } catch (SmackException.NotConnectedException | InterruptedException e) {
+        } catch (SmackException.NotConnectedException | InterruptedException | IllegalArgumentException e) {
             LOGGER.log(Level.WARNING, "Sending CSI state 'inactive' failed.", e);
         }
     }
diff --git a/entity/src/main/java/org/mercury_im/messenger/entity/contact/Peer.java b/entity/src/main/java/org/mercury_im/messenger/entity/contact/Peer.java
index 5bf74b0..9849763 100644
--- a/entity/src/main/java/org/mercury_im/messenger/entity/contact/Peer.java
+++ b/entity/src/main/java/org/mercury_im/messenger/entity/contact/Peer.java
@@ -2,6 +2,7 @@ package org.mercury_im.messenger.entity.contact;
 
 import org.mercury_im.messenger.entity.Account;
 
+import java.util.List;
 import java.util.UUID;
 
 import lombok.Data;
@@ -19,6 +20,7 @@ public class Peer {
     SubscriptionDirection subscriptionDirection;
     boolean subscriptionPending;
     boolean subscriptionApproved;
+    List<String> groupNames;
 
     public Peer() {
         this.id = UUID.randomUUID();